Novel gallium nitride doping by atomic layer deposition

Abstract

A device including an N-polar or metal-polar or semipolar or nonpolar III-Nitride semiconducting layer deposited by atomic layer deposition, and method of making the same. A device including a III-Nitride semiconducting layer deposited by atomic layer deposition and including an n-type or p-type dopant concentration of at least 1.3 × 1018 cm-3 and such that the layer has a mobility of at least 7 cm2 / V-s, and method of making the same.

Description

[0001] NOVEL GALLIUM NITRIDE DOPING BY ATOMIC LAYER DEPOSITION

[0002] CROSS REFERENCE TO RELATED APPLICATIONS

[0003] This Application claims the benefit under 35 U.S.C Section 119(e) of co-pending and commonly-assigned U.S. Provisional Patent Application No. 63 / 696,960 filed September 20, 2024, by Boyu Wang, William Mitchell, Stacia Keller, and Umesh Mishra, entitled “NOVEL GALLIUM NITRIDE DOPING BY ATOMIC LAYER DEPOSITION,” which application is incorporated by reference herein.

[0004] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

[0005] This invention was made with government support under N00014-23-1-2880 awarded by the Office of Naval Research. The government has certain rights in the invention.

[0006] BACKGROUND OF THE INVENTION

[0007] 1. Field of the Invention.

[0008] The present disclosure relates to nitrides and methods of making the same.

[0009] 2. Description of the Related Art.

[0010] Gallium nitride (GaN) has emerged as a leading semiconductor material due to its high electron mobility, wide bandgap, large critical breakdown electric field, and high electron saturation velocity [1], and is consequently used in a wide range of applications such as light-emitting diodes [2], power amplifiers [3], and high electron mobility transistors [4] [5], With a strong built-in polarization field, GaN RF devices have demonstrated continuously improved RF performance by utilizing its nitrogenpolar orientation. Highly-scaled HEMTs have shown excellent current density over 2 A / mm with fr-Lo over 11 GHz- pm at an aspect ratio of ~4 [6], Furthermore, in deep recess HEMTs, a W-band power density of 8.84 W / mm with an associated power- added efficiency of 27.0% was exhibited [7], In these devices, low-resistance ohmic contacts between electron channel and electrodes are critical to improve device performance. They are generally grown by metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) at elevated substrate temperatures [8]

[0011] [9], It is preferable to use material growth / deposition techniques for adding semiconducting materials, insulators, and metals that are readily available in standard process lines. Processes requiring a lower thermal budget and ability to deposit onto a variety of substrate topography, enabling easier process integration for devices and circuits with newer functionalities, higher performance, and lower cost, are needed.

[0012] Atomic layer deposition (ALD) is a promising technique to offer high-quality, high-uniformity films with precise thickness control due to its self-limiting layer-by- layer surface growth mechanism at relatively low temperatures, usually below 500 °C

[0013]

[0010] , ALD GaN growth processes have been reported in the literature using various precursors such as GaCh, trimethylgallium (TMGa), and triethylgallium (TEGa) for the group III half cycle, and various nitrogen-containing gases, such as NH3 or N2 plasma

[0011]

[0012]

[0013]

[0014]

[0015] have been implemented in the plasma step for the group V half-cycle. These studies reveal the great promises of ALD for high-quality GaN film growth at low surface temperatures. Nevertheless, there is only one reported investigation on ALD GaN doping for higher-conductivity applications. The only report the inventors could find was the work of Zhang et al., where a measurable amount of film conductivity was improved by inserting thin ALD SiN layers in between thicker ALD GaN layers (known as “digital doping”). They utilized TMGa for the Gallium precursor, di(t-butyl amino)silane (BTBAS) for the Si precursor, and NH3 gas as the nitrogen-containing gas

[0016] , Maximum carrier concentrations on the order of 1018cm’3were obtained in 40 nm thick films at a doping ratio of one SiN layer per 4 GaN layers. However, the carrier mobility was limited to below 7 cm2 / V-s. The combination of a relatively low carrier concentration and low mobility result in a sheet resistance too high to be useful for device applications. We hereby present doping approaches that allow higher doping during ALD growth. Illustrative embodiments described herein include, but are not limited to, the following.

[0014] 1. A device comprising: one or more III-Nitride semiconductor layers deposited using atomic layer deposition, comprising n-type and / or p-type dopants with a dopant concentration of at least (or more than) 1.3E18 cm-3 and carrier mobility of at least 7 cm2 / V-s.

[0015] 2. The device of clause 1, wherein the dopants occupy empty spots or vacancies left by one or more Group-Ill precursor doses in the Ill-nitride semiconductor layers and / or form a separate layer on the layer of Group III element or on or between the III-Nitride layers, wherein a number of the empty spots or vacancies is process adjustable to modify electrical performance including the mobility.

[0016] 3. The device of clause 1 or 2, wherein the dopants comprise indium, silicon, oxygen, germanium, sulfur, magnesium, zinc, beryllium or an indium containing compound layer alone or in combination with at least one other co-dopant.

[0017] 4. The device of any of the clauses 1-3, wherein the III-Nitride layers comprise an N-polar or metal-polar or semipolar or nonpolar III-Nitride semiconducting layer.

[0018] 5. The device of any of the clauses 1-4, wherein one or more of the III- Nitride semiconductor layers have a resistivity of no more than 0. 6 ohm cm

[0019] 6. The device of any of the clauses 1-5, wherein the layers have atomically sharp interfaces and comprise one or more monolayers each comprising group III atoms, nitrogen atoms, or a combination of both.

[0020] 7. The device of any of the clauses 1-5, wherein the III-Nitride layers are conformal with an underlying surface comprising: inside and outside portions of a trench having an aspect ratio (height to width ratio) of at least 2 or a horizontal surface and a sidewall having an angle in a range of 0.1-90 degrees with respect to the horizontal surface. 8. The device of any of the clauses 1-7, further comprising a contact layer comprising the III-Nitride semiconductor layers.

[0021] 9. The device of clause 8, wherein the dopant concentration forms an ohmic contact with a metal layer.

[0022] 10. The device of clause 8 or 9, further comprising an active region, further comprising the contact layer between a metal layer and the active region, wherein the contact layer in contact having flat top surface and inclined sidewall conformal with the underlayer.

[0023] 11. The device of any of the clauses 1-10, wherein at least one of the III- Nitride semiconductor layers comprises a sub -saturation dose of Group III precursor tailored for the dopant concentration.

[0024] 12. A method of fabricating a device, comprising: depositing one or more III-Nitride semiconductor layers using atomic layer deposition in a presence of dopants under conditions to form the one or more III- Nitride layers having a dopant concentration of at least 1.3E18 cm-3 and a carrier mobility of at least 7 cm2 / V-s.

[0025] 13. The method of clause 12, wherein the depositing comprises forming at least one of the layers using a sub-saturation dose of Group III precursor dose tailored for the dopant concentration; and exposing the one or more layers having the sub-saturation dose to the n-type or p-type dopants.

[0026] 14. The method of clause 12 or 13, wherein the dopants fill empty spots or vacancies formed in the layer with the sub-saturation dose, or and / or the dopants form a separate layer on the layer of Group III element or on or between the III- Nitride layers.

[0027] 15. The method of any of the clauses 12-14, wherein the III-Nitride semiconductor layers comprise an N-polar, semipolar, metal-polar, or nonpolar III- Nitride semiconducting layer. 16. The method of any of the clauses 12-15, wherein the depositing comprises:

[0028] (a) loading a substrate in a plasma enhanced ALD reactor;

[0029] (b) exposing a surface of the substrate to a group III material containing precursor using a saturated or sub-saturated dose to form a first layer on the surface;

[0030] (c) purging the reactor of the group III material containing precursor;

[0031] (d) exposing the first layer to a first plasma comprising a nitrogen containing gas or a nitrogen-containing gas without plasma to form the III -Nitride semiconductor layer;

[0032] (e) purging the reactor; exposure to a dopant precursor, comprising at least one of: providing the dopant precursor together with the group III material precursor in step (b) or after the purging step (c) but prior to step (d) to form the first layer, wherein the step optionally further comprises a purge of the dopant precursor immediately after exposure of the dose of the dopant precursor; or providing the dopant precursor after the step (d) but prior to the purging step (e), or providing the dopant precursor after the step (e)

[0033] 17. The method of clause 16, further comprising a second plasma step after step (d) and prior to step (e)

[0034] 18. The method of clause 16, wherein the temperature of the substrate during steps (b)-(e) is less than 500 degrees Celsius, the power of the plasma is above a first threshold level and a pressure in the reactor during steps (b)-(e) is below a second threshold level such that the III-Nitride semiconducting layer has a resistivity of no more than 0.6 ohm cm and a surface RMS roughness of no more than 10 nm over an area of 10 microns by 10 microns.

[0035] 19. The method of any of the clauses 12-18, wherein the group III precursor dosed for at least 1 microsecond, the first plasma comprises the nitrogen containing gas comprising ammonia and / or ammonia / nitrogen, and / or ammonia / hydrogen, and / or nitrogen, and / or nitrogen / hydrogen, the second plasma comprises nitrogen and / or argon, and the purging is with a gas comprising nitrogen and / or argon, the power is at least 1 W and up to 1E4 W, and the pressure is below 760 Torr.

[0036] 20. The method of any of the clauses 16-19, further comprising: depositing one or multiple cycles of steps (b)-(e) prior to exposure to a dopant cycle comprising the dopant precursor (including saturation or sub -saturation doses) followed by exposure to a plasma comprising a nitrogen containing gas.

[0037] 21. The method of any of the clauses 16-20, wherein the carrier gas for any of the precursors comprises at least one of hydrogen, nitrogen, or argon, and the purging gas comprises at least one of nitrogen or argon.

[0038] 22. The method of any of the clauses 12-21 , further comprising annealing the III-Nitride layer to control or modify the conductivity of the III-Nitride semiconductor layers.

[0039] 23. The method of any of the clauses 12-22, where the conductivity is modified locally, by local treatment of the III-Nitride semiconductor layer, for example, with a laser or an electron beam.

[0040] 24. The method of any of the clauses 16-23, comprising a plurality of cycles of the steps (b)-(e), wherein one or more of the steps (b) comprise a subsaturation dose of the group-III precursor and / or dopant precursor.

[0041] 25. The method of clause 24, wherein the sub -saturation dose is followed by the dopant precursor dose to increase dopant incorporation every time or after a pre-defined number of the cycles with a saturation dose of the group III precursor.

[0042] 26. The method or device of any of the clauses 1-29, wherein the III- Nitride semiconductor layers comprise a GaN layer and the device further comprises: a dielectric deposited by ALD on the GaN layer, or a metal layer deposited by ALD on the GaN layer, , e.g. ALD ruthenium, platinum, or aluminum. 27. The method or device of any of the clause 1-26, wherein the III- Nitride layers comprise a doped layer on an unintentionally doped layer and / or wherein a thin layer (0-5 nm) of unintentionally doped Ill-nitride layer can be added before or after any doping layers.

[0043] 28. The method or device of any of the clauses 12-27, further comprising performing a plasma-cleaning step before the atomic layer deposition.

[0044] 29. The method or device of any of the clauses 1-28, wherein: the layers are grown on either homogenous or heterogeneous surfaces including but not limited to Ill-nitride semiconductor layers, metal, and dielectric, and / or layers are on co-existing or contiguous planes of different orientations, for example, samples with patterned surfaces, of varying or similar polarizations in sign and magnitude or non-polar planes.

[0045] 30. The method of any of the clauses 1-29, wherein Indium is added during the ALD growth (at any steps) via Indium precursor doses, or after the growth via diffusion or implantation.

[0046] SUMMARY OF THE INVENTION

[0047] The present disclosure reports on optimization of ALD GaN film growth on Nitrogen-polar semi-insulating GaN, as well as investigation of various options for doping in ALD GaN films for conductivity enhancement. In particular, the present disclosure reports on the first (to Applicant’s knowledge) ALD growth of GaN films on nitrogen-polar GaN surfaces and first study of ALD GaN doping to improve electrical properties of Nitrogen-polar GaN films.

[0048] Atomic layer deposition has been demonstrated as being an excellent growth technique to achieve high-quality, high-uniformity, and high-conformality films, with its low growth temperature (< 500°C) and precise growth control due to a self-limiting surface growth mechanism on both homogenous and heterogenous surface. The present disclosure describes advanced ALD techniques for achieving high- quality low-resistance films. For instance, for Silicon doping: with or after a Gallium precursor dose, a Silicon precursor dose is introduced and purged, and then a Nitrogencontaining gas plasma is established to form Silicon-doped ALD GaN layers; for Oxygen doping, after a Gallium precursor dose and a Nitrogen-containing gas plasma, water vapor is dosed into the chamber. Promising results in our preliminary study are shown. For ~30 nm Si-doped ALD GaN film on GaN semi-insulating templates, we achieved around 4.0* 10'3Q-cm resistivity, 3.4* 1019cm’3charge density, and a carrier mobility of 44.4 cm2 / V-s. This is the first experiment ever conducted on N-polar GaN which shows remarkably better electrical properties than those reported via SiN “digital” doping method. Further improvements in film charge density were observed with charge densities up to 6* 1019cm’3after implementing a “dual-plasma” process and Gallium precursor sub-saturation dose cycles. The growth was conformal on the surface and no inferior growth modes occurred, which was confirmed by AFM and STEM. With optimization higher charge density is anticipated. One should note that the methods described herein are not limited to the materials or polar / orientation planes used in our experiments and can be applied to other available alternatives, suggesting that they have great potential and flexibility for general use in all ALD Ill-nitride systems.

[0049] BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0051] Referring now to the drawings in which like reference numbers represent corresponding parts throughout:

[0052] Figure 1 A Sketch of the semi-insulating GaN sample structure for the ALD growth study. Figure 2 Group III half-cycle saturation curve as a function of TEGa dose time.

[0053] Figure 3 10*10 pm2AFM scan showing the surface morphology with RMS roughness around 1.6 nm. Note that undulation appears due to a 4° miscut of the sapphire substrate.

[0054] Figures 4A-4B. Atomic Force Microscopy (AFM) images of samples Al (Figure 4A)and A2 (Figure 4B), both exhibiting less than 3.2 k / sq

[0055] Figures 5A-5C. Flows chart of the ALD doping methods according to embodiments described herein, wherein Figure 5A shows method (1) wherein the dopant dose is before the plasma step, Figure 5B shows method (2) wherein dopant dose is after the plasma step, and Figure 5C shows method (3) inserting an additional gas plasma after the Nitrogen-containing gas plasma. For Group III dose, sub-saturation dose cycle(s) can be inserted.

[0056] Figures 6A-6B. AFM images of two samples on N-polar semi-insulating GaN (A3 in Figure 6A and A4 in Figure 6B).

[0057] Figure 7A. STEM image showing good crystal quality of the ALD Silicon- doped GaN layer.

[0058] Figure 7B. EDS line scan of Silicon atoms across the ALD GaN doped layer exhibiting that Silicon is incorporated and contributes as the dopants.

[0059] Figure 7C. EDS map of a sample showing uniform silicon distribution as the dominant dopant.

[0060] Figure 7D. Si-doped GaN film resistivity and charge density versus nitrogen plasma time in a dual plasma process.

[0061] Figure 7E. Film resistivity and charge density dependence on sub-saturation TEGa dose percentage (at 100 ms sub-saturation dose)(Figures C-E reproduced from

[0018] ).

[0062] Figure 8 Example of multiple layer material stack grown on a template by

[0063] ALD. Figure 9. Example GaN planar HEMT device structure with contact regions deposited by ALD.

[0064] Figure 10A. Example of ALD layer trench sidewall and bottom deposition.

[0065] Figure 10B. example of ALD layer trench bottom deposition through selective area growth.

[0066] Figure IOC. an SEM image of ALD GaN selective area growth done using the proposed method.

[0067] Figure 11 Conformal ALD contact layers in a hypothesized device. The ALD layers are conformal to the structures beneath.

[0068] DETAILED DESCRIPTION OF THE INVENTION

[0069] In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

[0070] Technical Description

[0071] I. ALD GaN Growth Experiments

[0072] We first focused on ALD GaN growth to achieve films of acceptable quality before performing any doping studies. ALD GaN films were deposited on semiinsulating (S.I.) Nitrogen-polar GaN templates, composed of -110 nm unintentionally doped (UID) GaN and 1.5 pm S.I. GaN (iron doped), on 4° miscut sapphire substrate grown by MOCVD at University of California, Santa Barbara (the epi structure is illustrated in Figure 1). The samples were then diced into 1*1 cm2square pieces for ALD GaN growth experiments. Prior to ALD growth, each sample template underwent solvent clean with acetone, isopropyl alcohol, and deionized water under ultrasonic agitation. After the solvent clean, the sample was ozone-cleaned, followed by a HF clean and DI rinse. The cleaning procedure removes surface particulates, contaminants, and oxides.

[0073] The ALD GaN growth studies were conducted in an inductively coupled plasma (ICP) enhanced atomic layer deposition system (FlexAL, Oxford Instruments which reference is incorporated by reference herein). TEGa was used for the group III half-cycle, whereas high-purity NH3 and / or N2 as the nitrogen-containing gases for the nitride plasma step in the group V half-cycle. In addition, high-purity N2 or H2 (promoting NH3 dissociation

[0011] ) are used as carrier gases, and Ar and / or N2 as purge gases.

[0074] Each ALD GaN growth cycle includes four main steps: (1) TEGa dose; (2) gas purge; (3) Nitrogen-containing plasma, e.g., NH3 / N2, NH3 / H2, or N2 / H2; (4) gas purge. In the ALD GaN growth optimization experiment, TEGa dose time was maintained at 500 milliseconds (ms) based on the dose saturation curve study (Figure 2), while variables included plasma power, pressure, gas flow rate, and carrier gas (e.g., N2 or H2). The GaN films were deposited at 300°C. Si monitor pieces were also loaded with the N-polar GaN S.I. templates to allow easier ex-situ film thickness and refractive index measurements using a Woollam M-2000DI Variable Angle Spectroscopic Ellipsometer.

[0075] ALD GaN surface morphology was characterized by a Bruker ICON Atomic Force Microscope and film crystallinity was measured via X-Ray Diffraction (XRD) using a Philips X’PERT MPD system. Electrical measurements on the ALD GaN films, including film resistivity, charge density, and carrier mobility, were carried out using a LakeShore 7504 Hall System.

[0076] Table 1 shows Hall electrical measurements and surface roughness by AFM from the preliminary experiments for ALD GaN film growth on Nitrogen-polar GaN S.I. substrates at 300 C. Variables include gas plasma power, plasma pressure, and gas flows.

[0077] Table I Results of Preliminary Al J) GaN Growth at 30(t C

[0078] As observed, the ALD grown GaN films exhibited unintentionally n-type doped behavior due to impurities and / or native defects

[0017] , Table 1 shows that film resistivity was not significantly affected by changing gas plasma power and gas ratios. However, the data shows that higher gas plasma pressures, such as 20 and 50 mTorr, led to increased film resistivities by one or two orders of magnitude.

[0079] It was discovered that performing an ALD chamber clean with a plasma, e.g., oxygen-containing plasma, prior to an ALD GaN growth can result in reductions in unintentional doping or impurity incorporation, because it is speculated that the plasma helps remove some impurities in the chamber to be incorporated into the ALD GaN films. Table 2 shows electrical properties and film roughness of examples of the ALD GaN growth after an oxygen-containing plasma chamber clean. Compared to the results shown in Table 1, film conductivity was reduced by at least one order of magnitude.

[0080] Table 2 Results of ALD GaN Growth at 300 C after an Oxygen-containing plasma chamber clean

[0081] Based upon the above results above, a semi -optimized ALD GaN growth recipe in our FlexAL system for the initial doping experiments (with growth rate ~ 0.5 A per cycle) was as follows:

[0082] • Group III half-cycle: precursor: TEG (vapor draw), time = 500 ms, pressure = 750 mTorr.

[0083] • Group V half-cycle: plasma conditions: power = 400 W, NH3 / H2 gas flow = 60 / 40 seem, pressure = 10 mTorr, time = 15s (results in saturated ALD growth)

[0084] Figure 3 shows a 10*10 pm2AFM scan of the ALD regrown GaN surface with this recipe, with an RMS roughness of around 1.6 nm. It is noteworthy that this is the first time ALD GaN growth on N-polar GaN surfaces has been reported.

[0085] II. ALD GaN Growth with Doping

[0086] 1. SiN digital doping method

[0087] Zhang et al. reported that the use of ALD “digital doping”, i.e., inserting a SiN sub-cycle in between many GaN cycles, results in a charge density increase within the ALD GaN film

[0016] , They found however that even at charge densities of 1.29* 1018cm’3, the mobility was very low (below 7 cm2 / V-s).

[0088] To verify the feasibility of doping in the ALD tool, a similar doping method was first conducted. Two major changes were made compared to Zhang et al ,’s work:

[0089] 1) Nitrogen-polar GaN S.I. templates were used, and

[0090] 2) the Silicon precursor bis(diethylamino)silane (BDEAS) was used for doping. The process contained two independent loops: loop 1 (GaN): (1) TEGa dose; (2) N2 and / or Ar purge; (3) NH3 / H2 plasma; (4) N2 and / or Ar purge; and loop 2 (SiN): (5) BDEAS dose (500 ms); (6) N2 and / or Ar purge; (7) NH3 / H2 plasma; (8) N2 and / or Ar purge.

[0091] Loop 1 ran multiple times with loop 2 inserted once in between to produce a SiN “digital doping” layer. Table 3 summarizes the results for such GaN films.

[0092] Table 3 Summary of "Digital Doping" via BDEAS and NH3 plasma

[0093] Sample Al with 6 GaN cycles per single SiN cycle generated ALD GaN films exhibiting electrical properties that were superior to those reported by Zhang et al - a resistivity of 8.88* 10'3Q-cm, a mobility of 65.0 cm2 / V-s and a charge density over 1019cm’3. Increasing the GaN cycles from 6 to 8 slightly improved film conductivity. Figure 4 shows the AFM images of the two samples. Notably, this is the first report of conductivity enhancement via doping demonstrated for ALD GaN growth on N-polar GaN templates.

[0094] 2. Alternative Doping methods

[0095] Proposed new methods of ALD GaN doping for each ALD cycle are described below (Figure 5).

[0096] Method 1 : Ga-precursor dose flows (a) together with a “dopant” dose, or (b) the “dopant” dose being after the Ga-precursor dose and gas purge, followed by a Nitrogencontaining gas plasma, e.g., NH3, N2, or a combination of NH3, N2, and / or H2.

[0097] Method 2: the “dopant” dose is placed after a Nitrogen-containing gas plasma.

[0098] Method 3: after the Nitrogen-containing gas plasma in Method 1, another plasma step is added, e.g., N2 or Ar plasma before gas purge. Note that for the Group III dose step, sub -saturation dose cycles (determined by the dose saturation curve) can be inserted between saturation dose cycles to improve ALD GaN film conductivity. The choices of Ga-precursor include but are not limited to TEGa, TMGa, and trisfdimethyl amido]Ga (TDMAG), while the choices of purge gas include but are not limited to N2 and Ar.

[0099] “Dopant” sources in Method 1 include, but are not limited to, BDEAS or BTBAS (Si-precursor, as Si-doping), tertiary-butyl-germane (t-BGe) or isobutylgermane (IBGe) (Ge-precursor, as Ge-doping), diethyl zinc (Zn-precursor, as Zn p-type doping), and bis(cyclopentadienyl)magnesium (Cp?Mg) or bis(ethylcyclopentadienyl)magnesium (Mg(EtCp)2) (Mg-precursor, as Mg p-type doping). “Dopant” sources in Method 2 include but are not limited to water vapor (as oxygen-doping). Note that this technique is also applicable to heterojunctions and on materials which have simultaneously multiple planes exposed, such as planes of multiple polarizations in sign and magnitude, or non-polar planes.

[0100] Without being bound by a particular scientific theory, one mechanism hypothesized is that dose from dopant precursors can fill empty spots left by the group- ill precursor dose to become active dopants. More empty spots are anticipated if a subsaturation dose of the group-III precursors is implemented to increase further doping efficiencies.

[0101] Methods 1, 2, and 3 have been developed and proven workable. Gallium- precursor TEGa, purge gases N2 and / or Ar, Nitrogen-containing gas NH3 were used for studies in all methods. Silicon -precursor BDEAS was used for Method 1 and 3, and oxygen-source water vapor was used for Method 2.

[0102] Table 4 and Table 5 list the initial results of the Silicon and Oxygen doping study, respectively, showing film thickness, sheet resistance, charge density (sheet charge density / film thickness), carrier mobility, and surface roughness determined by AFM. For all the tests, 600 cycles were used to obtain doped GaN films with a thickness of around 30 nm. Si-doped ALD GaN films exhibited lower sheet resistances and demonstrated good reproducibility, with 4.00* 10'3Q-cm resistivity and 3.45* 1019cm’3charge density achieved. This is, to our knowledge, the first demonstration of ALD bipolar GaN doping.

[0103] To facilitate the initial growth, one may regrow 2-3 nm of unintentionally doped GaN before doping. As an extended study of the novel ALD doping method, a metal- polar semi-insulating sample (Gl) was applied Method 1(b) and showed good electrical properties as well — a resistivity of 1.7* 10’2Q-cm and a charge density of 8.15>< 1017cm’3. The film electrical conductivity and film quality can be further improved via ALD process optimization. As a reference, high-quality MBE GaN n+ regrowth on the N- polar semi-insulating sample produces a charge density of 1.54* IO20cm’3and a bulk resistivity of 5.4* 10'4Q-cm. AFM surface scans of samples A3 and A4 are shown in Figure 6.

[0104] Table 4 Summary of Silicon Doping Study by BDEAS (Method 1(b))

[0105] Table 5 Summary of Oxygen Doping Study by Water Vapor (Method 2)

[0106] S

[0107] In addition, the charge density and sheet resistance of the ALD GaN film show only slight change after dielectric deposition by plasma enhanced chemical vapor deposition (PECVD) at 300 °C, proving the reliability and compliance of the proposed

[0108] ALD doping method in other fabrication processes, see Table 6.

[0109] Table 6 ALD Doping GaN Film Stability Test Before and After PECVD Dielectric

[0110] Deposition

[0111] Moreover, the charge and conductivity of the ALD n-GaN films can be controlled via annealing, as seen in Table 7. Thereby, the ALD doped film conductivity can be locally modified via local heating down to a micro- and nanometer scale, for example, via exposing the ALD grown GaN layer to a laser beam or an electron beam.

[0112] Table 7 Annealing Test of ALL) GaN Doped Films by BDEAS

[0113] 3. Additional ALD GaN Doping Results 1181 Based on the preliminary ALD GaN growth studies, additional doping experiments were carried out with the following recipe / conditions to explore higher film conductivity while maintaining a good film crystal quality:

[0114] • Group III half-cycle: 500 ms TEGa dose time at 750 mTorr;

[0115] • Group V half-cycle: 15 s plasma dose time using NH3 / N2 flows of 90 / 40 seem at 10 mTorr chamber pressure and 400W power.

[0116] Table 8 lists some results of the extended doping study of ALD grown GaN films. 19

[0117] A charge density of 3.54x 10 was achieved with a carrier mobility of ~ 30 cm2 / V-s using Method 1(b) described above. Moreover, when Method 3(b) or “dual plasma”, i.e., adding an N2 plasma (flow = 100 seem) immediately after the nitrogen-containing plasma for 5 seconds, was performed for each ALD GaN doping cycle on sample D2, the charge density was improved to 4.88* 1019cm’3, and the sheet resistance was reduced to 1.05 kQ / sq. Note that a good surface morphology was retained. On this sample, Scanning Transmission Electron Microscopy (STEM) showed good crystal 5 structures in the ALD doped GaN film, verifying the high-quality ALD doping growth.

[0118] Also, an energy dispersive spectroscopy line scan proved a uniform distribution of Silicon in the film as the dopant (Figure 7). In addition, with the adoption of TEGa sub-saturation dose (one cycle for every 5 saturation dose cycles), where it is speculated that more sites are available on the surface for Si from the BDEAS dose to occupy 0 surface sites and act as dopants, the charge density was further enhanced to 6* 1019cm’

[0119] 3, with a carrier mobility of 37 cm2 / V-s. Remarkably, it was demonstrated that ohmic contacts were achievable to the ALD GaN doped films. These results encourage further research study on ALD doping GaN growth.

[0120] Table 8 Summary of Additional ALD Sitieim Doping Study by BDEAS

[0121] Sa 5

[0122] The promising results demonstrated the great feasibility of the methods described herein. It is emphasized that the methods disclosed herein can contribute to various applications, including material systems, material planes, doping type and concentration, and device applications, which are not limited to the materials above0 mentioned. For example, a p-type or n-type doping in one or multiple Ill-nitride semiconductor layers of different conductivity via the methods described herein can be performed on different materials (e.g., different Ill-nitride semiconductor layers and their alloys, metal, dielectric) and material planes of single or contiguous orientations (e.g., semi-polar, non-polar, nitrogen or metal-polar).

[0123] 4. Addition of Indium

[0124] Indium co-doping has been reported to enhance the conductivity of AlGaN:Si layers grown by MOCVD previously

[0019] , most likely through passivation of unintentional acceptors in the epitaxial layers. Similarly, the addition of indium or insertion of InGaN:Si layers resulted in a significant improvement of the conductivity of poly crystalline GaN:Si layers grown by MOCVD on glass

[0020] , In the ALD growth process, Indium can be introduced using the precursors TMIn, TEIn, or any other suitable Indium compound. In a further embodiment, the ALD GaN:Si can be replaced by ALD InGaN:Si or InN:Si, including layers, where the composition is graded from GaN to InN. Ultralow resistance ohmic contacts to two-dimensional electron gasses (2DEGs) in N-polar transistors were demonstrated using MBE as growth technique for such graded contact layers, with a record low contact resistance of 27 Qpm

[0021] , (In,Ga)N:Si / GaN:Si or (In,Ga)N:Si / (In,Ga)N:Si bi- or multi-layer structures can also be used as contact layers.

[0125] In the case of high Indium composition InGaN and InN layers, the conductivity can be sufficient to obtain low resistance ohmic contacts without additional Si doping. Furthermore, the conductivity of high Indium composition InGaN and InN layers was found to be less dependent on the crystalline perfection compared to GaN

[0020] , As the band gap decreases with increasing Indium content, more and more defect states move into the conduction band, allowing the fabrication of high n-type conductivity layers.

[0126] On the other hand, with the band gap decreasing with increasing Indium content, the acceptor doping levels move closer to the valence band, decreasing the acceptor activation energy and increasing the doping, as has been shown for InGaN:Mg. Similarly, higher p-type carrier concentrations are expected for p-InGaN compared to p-GaN deposited by ALD. Potential p-type dopants are magnesium (Mg) and zinc (Zn), but also beryllium (Be). Mg is typically supplied as Cp2Mg, Zn as diethyl zinc, but any suitable precursor can be used as dopant.

[0127] Embodiment variations

[0128] From the studies we have done and described herein, illustrative embodiments include, but are not limited to:

[0129] 1) Materials used for the herein-described methods are not limited to the abovementioned, other n- or p-type dopant sources / precursors (e.g., BDEAS, IBGe, diethyl zinc, and Cp2Mg) in various Ill-nitride systems (e.g., GaN, AIN, InN, BN, their alloys, and alloys with other material, e.g., scandium and yttrium) with different group- ill sources / precursors (including but not limited to TEGa, TMGa, TDMAG, TMIn, and TMA1) are feasible, which greatly expand the flexibility and functionality of the methods described herein.

[0130] 2) A wide variety of Nitrogen sources (e.g., NH3 and / or N2 plasma, N2H4), carrier gas (e.g., N2, H2, Ar), and purging gas (e.g., Ar, N2) can be implemented (options are not limited to above-mentioned).

[0131] 3) The methods described herein are practical to grow on either homogenous or heterogeneous surfaces including but not limited to Ill-nitride semiconductor layers, metal, and dielectric. In addition, the growth of doped material by ALD is not limited to the nitrogen-polar orientation, i.e., it is applicable to growth on metal-polar or non- and semi-polar surfaces as well. In addition, it is viable on structures with one or co-existing or contiguous planes of different orientations, for example, samples with patterned surfaces, of varying or similar polarizations in sign and magnitude or non-polar planes.

[0132] 4) The described method(s) can produce MOSFETs in III-N materials with controllable threshold voltage and channel mobility on one or multiple coexisting planes. 5) The described method(s) are compatible with ALD in-situ growth of dielectrics (e.g., SiN, SiCh, AI2O3) and metals.

[0133] 6) The described method(s) can be used to produce MOS channels with in- situ grown III-N heterojunctions followed by dielectrics and conductive materials including but not limited to metals.

[0134] 7) The described method(s) are compatible with other process steps involving PECVD dielectric deposition.

[0135] 8) Parameters in the herein-described methods can be tuned for different purposes, e.g., varying the film conductivity from n-type of different magnitude to insulating, or p-type with different magnitude.

[0136] 9) Multiple layer material stacks can be grown with varying material and / or doping concentration, for example, n-GaN followed by n-AlGaN, on a planar film surface or patterned surfaces with multiple co-exiting planes where the material composition and doping may or may not be the same. An example is illustrated in Figure 8.

[0137] 10) A thin layer (0-5 nm) of unintentionally doped III -nitride can be added before doping, while a hold can be applied after “dopant” dose to modulate dopant incorporation and activation.

[0138] 11) A plasma step can be applied in between group-III dose and “dopant” dose in Method 1(b), where H2 can be used as the plasma source (but not limited to) to help modulate dopant incorporation and activation.

[0139] 12) After the NH3 plasma step illustrated in Method 1, another plasma step can be applied (“dual-plasma” step, Method 3) to promote surface morphology and conductivity, where N2 can be used as a plasma source (not limited to N2).

[0140] 13) Modifying the group-III and / or dopant precursor half-cycle by utilizing sub-saturation doses of the group-III precursor (determined by the dose saturation curve) followed by the dopant precursor dose to increase dopant incorporation within the film. This modified half-cycle can either be used every time in place of a standard ALD cycle with a saturated dose or after a pre-defined number of these standard ALD cycles. Likewise, sub-saturation doses can be used for dopant precursors.

[0141] 14) Conductivity can be controlled by annealing at elevated temperatures, and local annealing control can be introduced to create regions of conductivity different from the as-grown samples.

[0142] 15) Indium can be added 1) during the Ill-nitride semiconductor layer growth as a co-doping with other dopants, or 2) after the Ill-nitride semiconductor layer growth, e.g., by thermal diffusion or implantation. These can modify defects, including native point defects in the film, to improve film quality and thermal stability.

[0143] 16) ALD GaN with Silicon-doping can be replaced by ALD InGaN or InN with Silicon doping, where the composition is graded from GaN to InGaN or InN. (In,Ga)N:Si / GaN:Si or (In,Ga)N:Si / (In,Ga)N:Si bi- or multi-layer structures can also be used as contact layers.

[0144] 17) The ALD film conductivity can be sufficient to obtain low resistance contacts without additional Silicon doping in the case of high Indium contents in InGaN or InN layers.

[0145] 18) Higher ALD InGaN film p-type conductivity can be achieved by Mg doping, or other p-type dopants in InGaN. Potential p-type dopants include Mg (e.g. Cp2Mg), Zn (e.g., diethyl zinc), and Be.

[0146] 19) A plasma-involved cleaning procedure can be performed before the ALD Ill-nitride semiconductor layer growth.

[0147] 20) Any combinations of Method 1-3 can be performed together, and individual steps can be exchanged, added, or removed during each ALD cycles. Parameters for each step can be adjusted.

[0148] 21) The method or devices of any of the clauses combined or performed using any of the examples 1-20 above.

[0149] 22) P-type (In,Ga)N by ALD

[0150] The herein described methods are efficient in achieving high-quality ALD GaN films with controllable conductivity for various applications at reduced cost and process complexity, demonstrating ALD as a strong candidate among other growth techniques such as MOCVD and MBE for III-N materials.

[0151] Example Device Structure

[0152] Figure 9 shows a transistor device where ALD is not used to deposit the epitaxial layers (active layer, barrier layers, or buffer layer, etc.) but rather to deposit only the Ill-nitride in the contact regions, e.g., transistor source and drain. The device layers such as active layer / channel, barrier layer can be grown by MOCVD or MBE, and then the contact regions can be deposited by ALD with various conductivities. Figure 9 shows that the n+ GaN and / or UID GaN beneath the Source and Drain metal pads can be deposited by ALD. Additionally, contact regions in other devices, such as LEDs, lasers, solar cells, or photodetectors, can also be deposited by ALD.

[0153] Additional figures are used to illustrate the feasibility of ALD GaN layers in various device structures. Figure 10 shows examples of ALD growth in high aspect ratio device structures. Figure 11 shows an example of conformal ALD contact layers grown in a hypothesized device. The device comprises a substrate 502 (e.g., may include buffer layer, nucleation layer, and substrate), a channel layer with 2DEG / 2DHG on the substrate, one or more layers 504 on the channel layer, e.g., layers 504 can comprise n+ layer grown by MBE or MOCVD, or n- or UID GaN layer, or an n+ layer on top of an n- or UID GaN layer), and ALD layers 506 showing that we can add multiple ALD layers that are conformal to the underlying structures.

[0154] Further Device Embodiments

[0155] Illustrative embodiments described herein include, but are not limited to, the following.

[0156] 1. A device comprising: one or more (e.g., uniform and conformal) III-Nitride semiconductor layers, e.g., as characterized by deposition using atomic layer deposition, comprising n-type or p-type dopants with a dopant concentration of at least 1.3E18 cm’3and carrier mobility of at least 7 cm2 / V-s.

[0157] 2. The device of clause 1, wherein the dopants occupy empty spots left by one or more Group-Ill precursor doses in the Ill-nitride semiconductor layers and / or form a separate layer on the layer of Group III element or on the III-Nitride layers, wherein a number of the empty spots is process adjustable to modify electrical performance including the mobility.

[0158] 3. The device of clause 1, wherein the dopants comprise indium or an indium containing compound alone or in combination with at least one other codopant.

[0159] 4. The device of clause 1, wherein the III-Nitride layers include a layer of Gallium Nitride, a layer of GaN and InGaN, a graded stack with varying Indium composition from GaN to InN, a layer of GaN and AlGaN, or a graded stack varying, from GaN to AIN. .

[0160] 5. The device of clause 1, wherein the III-Nitride layers comprise an N- polar or metal-polar or semipolar or nonpolar III-Nitride semiconducting layer.

[0161] 6. The device of clause 1, wherein the III-Nitride semiconductor layers each have at least one of a thickness unform to within 10% across an entire surface area of the layers (in the case of planar surfaces), a resistivity of no more than 0. 6 ohm cm or a surface RMS roughness of no more than 10 nm over an area of 10 microns by 10 microns (in the case of planar surfaces).

[0162] 7. The device of clause 1, wherein the III-Nitride layers are conformal with an underlying surface comprising: inside and outside regions of a trench having an aspect ratio (height to width ratio) of at least 2 or a horizontal surface and a sidewall having an angle in a range of 0.1-90 degrees or 10-90 degrees with respect to the horizontal surface.

[0163] 8. The device of clause 1, further comprising a contact layer comprising the III-Nitride semiconductor layers. 10. The device of clause 8, wherein the doped contact layer? forms an ohmic contact with a metal layer.

[0164] 11. The device of clause 1, wherein at least one of the III-Nitride semiconductor layers comprises a sub -saturation dose of Group III precursor tailored for the dopant concentration.

[0165] 12. A method of fabricating a device, comprising: depositing one or more III-Nitride semiconductor layers using atomic layer deposition in presence of dopants under conditions to form the one or more III-Nitride layers having a dopant concentration of at least, or greater than, 1.3E18 cm’3(or in some examples, in a range of 1.3E18cm'3< dopant concentration < lE22cm'3and a carrier mobility of at least 7 cm2 / V-s (or in some examples 7 cm2 / V-s < mobility < 2500 cm2 / Vs)

[0166] 13. The method of clause 12, wherein the ALD growth comprises forming at least one layer using a sub-saturation dose of Group III precursor dose tailored for the dopant concentration; and exposing the one or more layers having the sub-saturation dose to the n-type or p-type dopants.

[0167] 14. The method of clause 12 or 13, wherein the dopants fill empty spots formed in the layer with the sub-saturation dose or a separate layer on or between the layers.

[0168] 15. The method of clause 12, wherein the III-Nitride semiconductor layers comprise an N-polar, semipolar, metal-polar, or nonpolar III-Nitride semiconducting layer.

[0169] 16. The method of clause 12, wherein the ALD growth comprises:

[0170] (a) loading a substrate in a plasma enhanced ALD reactor, e.g., wherein the substrate is configured for N-polar, semipolar, metal -polar, or nonpolar growth of Ill-ni tride; (b) exposing a surface of the substrate to a group III material containing precursor using a saturated or sub-saturated dose determined by dose saturation curve (precursor dose time v. growth rate) to form a first layer on the surface;

[0171] (c) purging the reactor of the group III material containing precursor , e.g., using nitrogen and / or argon gas;

[0172] (d) exposing the first layer to a first plasma comprising a nitrogen containing gas, or a nitrogen containing gas without plasma to form the III-Nitride semiconductor layer; wherein the nitrogen containing gas may be carried in a carrier gas comprising at least one of hydrogen, nitrogen, or argon, wherein the nitrogencontaining gas or its plasma interacts with the first layer, e.g., to form the N-polar, semipolar, metal-polar, or nonpolar III-Nitride semiconducting layer;

[0173] (e) purging the reactor; exposure to a dopant precursor, comprising at least one of providing the dopant precursor together with the group III material precursor in step (b) or after the purging step (c) but prior to step (d) to form the first layer, wherein the step optionally further comprises a purge of the dopant precursor immediately after exposure of the dose of the dopant precursor; or providing the dopant precursor after the step (d) but prior to the purging step (e), or providing the dopant precursor after the step (e)

[0174] 17. The method of clause 16, further comprising a second plasma step after step (d) and prior to step (e)

[0175] 18. The method of clause 16, wherein the temperature of the substrate during steps (b)-(e) is less than 500 degrees Celsius, the power of the plasma is above a first threshold level and a pressure in the reactor during steps (b)-(e) is below a second threshold level such that the III-Nitride semiconducting layer has a resistivity of no more than 0.6 ohm cm (e.g., in a range of 5E-5 ohm cm < resistivity < 0.6 ohm cm and a surface RMS roughness of no more than 10 nm over an area of 10 microns by 10 microns. 19. The method of any of the clauses 12-18, wherein the group III precursor (e.g., but not limited to TEGa, TMGa, TDMAG, TMA1, TMIn) dosed for at least 1 microsecond, the first plasma comprises the nitrogen containing gas comprising ammonia and / or ammonia / nitrogen, and / or ammonia / hydrogen, and / or nitrogen, and / or nitrogen / hydrogen, the second plasma comprises nitrogen and / or argon, and the purging is with a gas comprising nitrogen and / or argon, the power is at least 1 W, and the pressure is below 760 Torr.

[0176] 20. The method of any of the clauses 16-18, further comprising: depositing one or multiple cycles of steps (b)-(e) prior to exposure to a dopant cycle comprising the dopant precursor (including saturation or sub -saturation doses) followed by exposure to a plasma comprising a nitrogen containing gas.

[0177] 21. The method of any of the clauses 16 to 20, wherein the dopant precursor (e.g., at least one of indium, silicon, oxygen, germanium, indium, zinc, or magnesium (e.g., TMIn, BDEAS, BTBAS, TDMAS, t-BGe, IBGe, diethyl zinc, Cp2Mg, Mg(EtCp)2), or any group IV and VI elements in periodic table, or compounds thereof (e.g., oxygen in the form of water vapor, or EES or indium containing compounds).

[0178] 22. The method of any of the clauses 16-18, wherein the carrier gas for any of the precursors comprises at least one of hydrogen, nitrogen, or argon, and the purging gas comprises at least one of nitrogen or argon.

[0179] 23. The method of any of the clauses 16-18 compatible with in-situ ALD dielectric deposition comprising e.g., SiCE, SiN, HfCE, or AI2O3, and metal deposition comprising e.g., ruthenium, platinum, or aluminum. The ALD dielectric or metal deposition is durable before or after the ALD deposition, either in-situ, or do any of these deposition after a certain time, and the deposition temperature of these materials can be different.

[0180] 24. The method of any of the clauses 16-18 is compatible with PECVD dielectric deposition growth temperatures e.g., for materials comprising SiCh or Si3N4. 25. The method of any of the clauses 12-24 , further comprising annealing the III-Nitride layer to control or modify the conductivity of the III-Nitride semiconductor layers.

[0181] 26. The method of any of the clauses 12-25, where the conductivity is modified locally, by local treatment of the III-Nitride semiconductor layer, for example, with a laser or an electron beam.

[0182] 27. The method of any of the clauses 16-26, comprising a plurality of cycles of the steps (b)-(e), wherein one or more of the steps (b) comprise a subsaturation dose of the group-III precursor and / or dopant precursor.

[0183] 28. The method of clause 27, wherein the sub -saturation dose is followed by the dopant precursor dose to increase dopant incorporation every time or after a pre-defined number of the cycles with a saturation dose of the group III precursor.

[0184] 29. The method or device of any of the clauses 1-29, wherein the III- Nitride semiconductor layers comprise a GaN layer and the device further comprises: a dielectric, e.g. ALD silicon nitride, silicon oxide, or aluminum oxide, deposited by ALD on the GaN layer, or a metal layer deposited by ALD on the GaN layer, , e.g. ALD ruthenium, platinum, or aluminum.

[0185] 30. The method or device of any of the clauses 1-29, wherein the III- Nitride semiconductor layers comprise a GaN layer and at least one of an AIN, Al GaN, InN, InGaN layer.

[0186] 31. The method or device of any of the clause 1-30, wherein the III- Nitride layers comprise a doped layer on an unintentionally doped layer.

[0187] 32. The method of any of the clauses 12-31, further comprising performing a plasma-cleaning step before the atomic layer deposition.

[0188] 33. The methods of any of the clauses can be applied to growth on either homogenous or heterogeneous surfaces including but not limited to Ill-nitride semiconductor layers, metals, and dielectrics. In addition, it is viable on structures with one or co-existing or contiguous planes of different orientations, for example, samples with patterned surfaces, of varying or similar polarizations in sign and magnitude or non-polar planes.

[0189] 34. The method or device of any of the clauses 1-33, wherein a thin layer (0-5 nm) of unintentionally doped Ill-nitride layer can be added before or after any doped layers.

[0190] 35. The method or device of any of the clauses 1-34, wherein Indium can be added during the ALD growth (at any steps) via Indium precursor doses, or after the growth via diffusion or implantation.

[0191] 36. The method of any of the clauses 1-35, wherein Ill-nitride semiconductor layers can be of different composition within the (B, Al,Ga,In,Sc,Y)N alloy system.

[0192] 37. The method of any of the clauses 1-36, further comprising: loading a substrate in a reactor; depositing one or multiple cycles of III-Nitride material on the N-polar, semi- polar, metal-polar, non-polar substrate by plasma enhanced atomic layer deposition, wherein each of the cycles comprise exposure to a group III nitride precursor (including saturation or sub-saturation doses) followed by exposure to a plasma comprising a nitrogen containing gas (e.g., ammonia, and / or ammonia / nitrogen, and / or ammonia / hydrogen, and / or nitrogen, and / or nitrogen / hydrogen gas), or a nitrogen containing gas without plasma; and depositing a cycle of dopant material on the III-Nitride material by plasma enhanced atomic layer deposition, wherein the cycle comprises exposure to a dopant precursor (including saturation or sub-saturation doses) followed by exposure to a plasma comprising a nitrogen containing gas, or a nitrogen containing gas without plasma.

[0193] 38. The method of clause 37, further comprising purging the reactor after each of the precursor exposure steps, e.g., using nitrogen and / or argon gas.

[0194] 39. The method of any of the clauses 12-38 , further comprising: a) loading a substrate in a plasma enhanced ALD reactor, wherein the substrate is configured for Ga-polar, N-polar, semipolar, metal-polar, or nonpolar growth of Ill-nitride; b) performing one or more cycles each comprising:

[0195] (i) exposing a surface of the substrate to a group III material containing precursor (including saturation or sub-saturation doses) and a dopant precursor (including saturation or sub -saturation doses) to form a first layer on the surface;

[0196] (ii) purging the reactor of the precursor, e.g., using nitrogen and / or argon gas; and

[0197] (iii) exposing the layer to a plasma comprising a nitrogen containing gas, or a nitrogen containing gas without plasma, wherein the nitrogen-containing gas or its plasma interacts with the layer to form the doped III-Nitride semiconducting crystal layer.

[0198] 40. The method of any of the clauses 12-37, further comprising: loading a substrate in a plasma enhanced ALD reactor; performing one or more cycles each comprising:

[0199] (i) exposing the substrate to a group III precursor (including saturation or subsaturation doses) to form a layer,

[0200] (ii) purging the reactor, e.g., using nitrogen and / or argon gas;

[0201] (iii)exposing the layer to a dopant precursor (including saturation or subsaturation doses) to form a treated layer;

[0202] (iv)purging the dopant precursor, e.g. using nitrogen and / or argon gas; and

[0203] (v) exposing the treated layer to a plasma comprising a nitrogen containing gas, or a nitrogen containing gas without plasma.

[0204] 41. The method of any of the clauses 12-37, further comprising: loading a substrate in a plasma enhanced ALD reactor; performing one or more cycles each comprising:

[0205] (i) exposing the substrate to a group III precursor (including saturation or sub-saturation doses) to form a layer, (ii) purging the reactor, e.g., using nitrogen and / or argon gas;

[0206] (iii) exposing the layer to a dopant precursor (including saturation or subsaturation doses) to form a treated layer;

[0207] (iv) purging the dopant precursor, e.g. using nitrogen and / or argon gas;

[0208] (v) exposing the treated layer to a plasma comprising a nitrogen containing gas, or a nitrogen containing gas without plasma; and

[0209] (vi) exposing the treated layer to a plasma comprising nitrogen or Argon gas, or a gas flow of nitrogen or argon.

[0210] 42. The method of any of the clauses 12-37, further comprising: loading a substrate in a plasma enhanced ALD reactor; performing one or more cycles each comprising:

[0211] (i) exposing the substrate to a group III precursor (including saturation or sub-saturation doses) to form a layer,

[0212] (ii) purging the reactor, e.g., using nitrogen and / or argon gas;

[0213] (iii) exposing the layer to a plasma comprising only hydrogen gas;

[0214] (iv) exposing the layer to a dopant precursor (including saturation or subsaturation doses) to form a treated layer;

[0215] (v) purging the dopant precursor, e.g. using nitrogen and / or argon gas; and

[0216] (vi) exposing the treated layer to a plasma comprising a nitrogen containing gas, or a nitrogen containing gas without plasma.

[0217] 43. The method of any of the clauses 12-42, wherein the dopant precursor comprises but not limit to e.g., silicon, germanium, indium, zinc, or magnesium.

[0218] 44. The method of any of the clauses 12-43 further comprising: loading a substrate in a plasma enhanced ALD reactor; performing one or more cycles each comprising:

[0219] (i) exposing the substrate to a group III precursor (including saturation or sub-saturation doses) to form a layer;

[0220] (ii) purging the reactor, e.g., using nitrogen and / or argon; (iii)exposing the layer to a plasma comprising a nitrogen containing gas, or a nitrogen containing gas without plasma to form a treated layer; and

[0221] (iv) exposing the plasma treated layer to a dopant precursor (including saturation or sub -saturation doses) to form the doped III-Nitride semiconducting layer.

[0222] 45. The method of any of the clauses 12-44, wherein the dopant precursor comprises group IV and VI elements in period table (e.g., oxygen in the form of water vapor, or H2S).

[0223] 46. The method of any of the clauses 12-45, wherein the group III precursor comprises e.g., TEGa, TMGa, trisfdimethyl amido]Ga (TDMAG), Trimethylaluminium (TMA1), or Trimethylindium (TMIn), the nitrogen precursor comprises e.g., ammonia, nitrogen, or nitrogen / hydrogen, the n-type dopant precursor / material comprises group IV and VI elements include Si-doping (e.g., silane, BDEAS, BTBAS, or Tris(dimethylamino)silane (TDMAS)), Ge-doping (e.g., tertiary-butyl-germane (t-BGe) or isobutylgermane (IBGe)), O-doping (e.g., water vapor), S-doping (e.g., H2S), or metal doping (e.g., Sn), and the p-type dopant precursor / materials comprises group II and IV elements include Mg-doping (e.g., bis(cyclopentadienyl)magnesium (Cp2Mg) or bis(ethylcyclopentadienyl)magnesium (Mg(EtCp)2)), Zinc-doping (e.g., diethyl zinc), and Be-doping.

[0224] 47. The method of any of the clauses 12-45, wherein the carrier gas comprises at least one of hydrogen, nitrogen, or argon, and the purging gas comprises at least one of nitrogen or argon.

[0225] 48. The method of any of the clauses 12-47 compatible with in-situ ALD dielectric deposition comprising e.g., SiCE, SiN, HfCE, or AI2O3, and metal deposition comprising e.g., ruthenium, platinum, or aluminum.

[0226] 49. The method of any of the clauses 12-48 compatible with PECVD dielectric deposition comprising e.g., SiCE or SislS . 50. A III-Nitride substrate or device (transistor or light emitting device or solar cell or photodetector) comprising III-Nitride comprising the device of clauses 1- 49 or deposited using the method of any of the clauses.

[0227] 51. The III-Nitride semiconducting layer of any of the clauses 1-71 having a resistivity of 0.6 Q cm or less, at least a 1.3 * 1018cm’3charge density, at least a mobility of 7 cm2 / V-s, a surface RMS roughness of 10 nm or less over an area of 10 microns by 10 microns.

[0228] 52. The III-Nitride semiconducting layer of any of the clauses 1-71 comprising or consisting of GaN.

[0229] 53. The III-Nitride semiconductor layer of any of the clauses 1-71 wherein the substrate comprises or consists of sapphire, silicon, silicon carbon, or Ill-nitride.

[0230] 54. The method or device of any of the clauses 1-71, further comprising annealing the III-Nitride layer to control or modify the conductivity of the ALD GaN film.

[0231] 55. The method or device of any of the clauses 1-71, where the conductivity is modified locally, by local treatment of the sample surface with, for example, a laser or an electron beam.

[0232] 56. The method or device of any of the clauses 1-71, further comprising modifying the group-III / dopant precursor half-cycle by utilizing a sub-saturation dose of the group-III precursor (e.g., less than 5000 ms) followed by the dopant precursor dose to increase dopant incorporation within the film. This modified half-cycle can either be used every time in place of the standard ALD cycle or after a pre-defined number of standard ALD cycles.

[0233] 57. The method or device of any clauses 1-71, wherein instead of one layer, layer stacks are deposited where the composition and / or conductivity in the individual layers is different.

[0234] 58. The method or device of any of the clauses 1-71, where on top of the ALD GaN layer, ALD AIN, AlGaN, InN, InGaN or any other Ill-nitride layer is deposited by ALD. 59. The method or device of any of the clauses 1-71, where instead of doped ALD GaN doped AIN, AlGaN, InN, InGaN or any other Ill-nitride layer or layer within the (B, Al,Ga,In,Sc,Y)(N,P,As,Sb) alloy system is deposited by ALD.

[0235] 60. The method or device of any of the clauses 1-71, where first an unintentionally doped ALD GaN layer is deposited followed by doped GaN.

[0236] 61. The method or device of any of the clauses 1-71 wherein the Ill-nitride semiconductor layer deposited by ALD is a contact layer to an epitaxial device layer grown by a different method (e.g., by metal organic chemical vapor deposition or molecular beam epitaxy).

[0237] 62. The method or device of any of the clauses 1-71, wherein the III- nitride semiconductor layer(s) comprise a contact layer that is a source contact region or a drain contact region in a transistor or any other contact region in an electronic device or optoelectronic device such as a laser or light emitting diode, photodetector, or solar cell.

[0238] 63. The method or device clause 62 wherein the contact layer comprises n+ GaN and / or UID GaN beneath the metal contacts (e.g, source and drain metal)

[0239] 64. The method or device of any of the clauses 1-71, wherein the III- nitride is grown by ALD on a substrate comprising N-polar Ill-nitride (e.g., N-polar GaN), sapphire, silicon, or silicon carbon.

[0240] 65. The method or device of any of the clauses 1-71, wherein the III- Nitride semiconductor layer are crystalline as grown at a temperature below 500 degrees Celsius and a pressure above 1 mTorr.

[0241] 66. The method or device of any of the clauses 1-71, wherein the III- Nitride layers are conformal to an underlayer comprising a three dimensional (3D) structure, a non-planar surface, or a surface having an aspect ratio (height to width) of at least 2 and / or are more conformal to the underlayer than if the layers were grown by MOCVD or MBE, e.g., under similar conditions. 67. The method or device of any of the clauses 1-71, wherein the interfaces and surfaces of the layers are characterized by self-limiting growth.

[0242] 68. The method or device of any of the clauses 1-71, wherein the interfaces between different composition nitride layers and / or between doped layers and non-doped layers, or between dopants and III-Nitride layers, are abrupt (atomic monolayer precision or transition from the material in one layer to the material in the next layer occurs in some examples within 1 monolayer or within 1 nanometer or within 5 nanometers), e.g., without dopant diffusion.

[0243] 69. The method of device of any of the clauses 1-71, wherein the interfaces are sharper than those formed that could be formed by MOCVD and MBE.

[0244] 70. The method or device of any of the clauses 1-71, comprising the ALD layers grown on an active region comprising InGaN, wherein the Indium content or compositional stoichiometry of the active layer is not thermally degraded.

[0245] 71. The method or device of any of the clauses 1-71, wherein the III- Nitride layers have a higher amount of carbon and / or oxygen impurities than the layers grown by MOCVD or MBE, e.g.. one or more of the III-Nitride semiconductor layers have an oxygen content of at least 0.1 at. % or at least 1 at.% or at least 0.1 %.

[0246] IV. Commercial Advantages

[0247] Gallium nitride has been developed as a promising semiconductor material for LEDs, power devices, and high electron mobility devices with its wide bandgap, high mobility, high breakdown field, and high electron saturation velocity. The market is projected to grow at a CAGR of 26.4% from 2024 to 2030. In these devices, high- quality doping layers such as for n+ contacts are necessary for enhanced performance. Traditionally, doping layers were grown by molecular beam epitaxy or metal-organic chemical vapor deposition where high temperature (above 700°C) is required, operation procedures can be complicated, and system maintenance can be cumbersome, limiting their utilization for devices sensitive to high-temperature, having high aspect ratio structures as in power and memory devices, or needing rapid low-cost production. Atomic layer deposition has been demonstrated as an excellent alternative with its low- temperature growth mechanism and precise growth control, i.e., layer-by-layer surfacelimiting growth, and simplified operation and maintenance procedures.

[0248] Reports are showing high-quality, high-uniformity, and high-conformality GaN films achieved by ALD, expanding its use in novel semiconductor devices where traditional high-temperature growth techniques rarely can compete with, e.g., in filmconformality, cost, and easiness of manipulation. However, there is a lack in studies on ALD growth of doped GaN films. Here we present methods for ALD GaN doping and have demonstrated over 5* 1019cm’3charge density in GaN films while maintaining good surface morphology in our preliminary study, suggesting that high-quality ALD GaN growth and doping have great prospects for being low-cost and robust in GaN- based devices, improving their structural and electrical properties. In parallel, it is a promising option compatible with traditional growth techniques, in line with the drastically growing need in GaN-based devices. Moreover, the versatility of ALD allows for the doping method(s) described herein to be flexibly implemented to other dopant sources, polar plane orientations, and material systems such as AIN, InN, and their alloys, thus providing pliable options to choose from, reducing cost and complexity, and increasing functionality and flexibility as compared to and as an excellent growth candidate to other growth techniques.

[0249] Differences between layers grown by Atomic Layer Deposition and other techniques such as Metal Organic Chemical Vapor Deposition (MOCVD) and Molecular Beam Epitaxy (MBE)

[0250] Atomic Layer Deposition (ALD) is a vapor-phase technique that can be characterized, in some examples, by sequential, self-limiting surface reactions occurring at temperatures which are lower compared to the typical deposition temperatures of epitaxial techniques such MOCVD and MBE . Each precursor can be introduced individually, allowing for the deposition of material in a layer-by-layer fashion with atomic-scale precision. Due to the low process temperatures the resulting films can exhibit exceptional conformality with the underlying topology (e.g., not adding additional surface roughness), even over substrates with high aspect ratios or complex topographies. Structurally, ALD-deposited layers are amorphous, polycrystalline, or crystalline, depending on the deposition temperatures, conditions and pre- and / or post-deposition thermal treatments. The interfaces formed by ALD can be abrupt and well-defined (e.g., the interface can be a line between two different atom layers) due to the self-limiting nature of the surface reactions, which minimizes intermixing between adjacent layers. Defect densities in ALD films are generally low, although grain boundaries may be present in polycrystalline variants. Due to the low temperature deposition (e.g., below 500 degrees Celsius) in some embodiments, the effects of thermal degradation of previously deposited layers such as InGaN can be minimized. Impurities (e.g., carbon) present during growth may be moderate in some examples but can also be reduced.

[0251] Embodiments of ALD also enables sharper dopant profiles due to atomic-scale control and minimal diffusion. The absence of hydrogen-rich environments during ALD in some embodiments reduces the likelihood of dopant passivation, and therefore resulting films tend to have better interface quality, particularly in ultra-thin or conformal layers.

[0252] Although the ALD layers were grown by Plasma ALD (group-III precursor and dopant doses were vapor drawn into the reaction chamber, while nitrogen source was in a plasma form), other types of ALD such as thermal ALD could be used.

[0253] MOCVD on the other hand employs volatile metal-organic precursors that decompose thermally upon contact with a heated substrate. This continuous flow process enables the growth of highly crystalline films, particularly for compound semiconductors such as GaN, InP, and AlGaAs. While MOCVD offers good control over film thickness and composition, its conformality is limited compared to ALD, especially on high-aspect ratio surfaces / structures. The interfaces produced by MOCVD are generally sharp but may exhibit some degree of interdiffusion or roughness depending on the process condition and the generally significantly higher growth temperatures compared to ALD. Defect densities in MOCVD-grown films are typically low, but can vary depending on lattice matching and growth conditions. In special cases, such as Mg in GaN, for example, MOCVD dopants can require high- temperature annealing to activate, which can lead to dopant diffusion and interface broadening. Therefore, interfaces between different layers and dopant layers are often less sharp or abrupt compared to ALD grown layers. MOCVD grown surfaces are typically characterized by atomic steps resulting from a step-flow growth mode.

[0254] MBE is a physical vapor deposition technique conducted under ultra-high vacuum conditions. Elemental sources are evaporated and directed toward the substrate, where atoms condense and form epitaxial layers. MBE enables the growth of singlecrystal films with atomically abrupt interfaces, making it ideal for quantum well structures and superlattices. However, MBE is inherently limited in conformality and is best suited for planar substrates. The deposition rate is slow, but the structural quality of the films is high. The precision of MBE allows for monolayer control over composition and thickness, facilitating the fabrication of complex heterostructures MBE may also be characterized by step flow epitaxial growth.

[0255] ALD grown layers as described herein may in some embodiments comprise lower crystallinity as compared to MBE and MOCVD, but have sharper interfaces (e.g., precise interfaces between different atomic layers including dopant layers) as compared to MOCVD and perhaps comparable to that produced by MBE. However, conformality of layers to underlying layers / structures having an aspect ratio (e.g., height / width at least 2) is higher for ALD layers as compared to MBE and MOCVD layers. Signature impurities that may, in some embodiments, be found in ALD layers as compared to MOCVD and MBE include carbon and oxygen impurities due to the very low deposition temperatures. In turn, the very low deposition temperatures allow the growth on thermally sensitive materials and layer structures.

[0256] Nomenclature GaN and its ternary and quaternary compounds incorporating aluminum and indium (Al GaN, InGaN, AlInGaN) are commonly referred to using the terms (Al,Ga,In)N, Ill-nitride, III-N, Group Ill-nitride, nitride, Group III-N, Al(i-x-y)InyGaxN where 0 < x < 1 and 0 < y < 1, or AlInGaN, as used herein. All these terms are intended to be equivalent and broadly construed to include respective nitrides of the single species, Al, Ga, and In, as well as binary, ternary and quaternary compositions of such Group III metal species. Accordingly, these terms comprehend the compounds AIN, GaN, and InN, as well as the ternary compounds AlGaN, GalnN, and AllnN, and the quaternary compound AlGalnN, as species included in such nomenclature. When two or more of the (Ga, Al, In) component species are present, all possible compositions, including stoichiometric proportions as well as “off- stoichiometric” proportions (with respect to the relative mole fractions present of each of the (Ga, Al, In) component species that are present in the composition), can be employed within the broad scope of the invention. Accordingly, it will be appreciated that the discussion of the invention hereinafter in primary reference to GaN materials is applicable to the formation of various other (Al, Ga, In,)N material species. Further, (Al,Ga,In)N materials within the scope of the invention may further include minor quantities of dopants and / or other impurity or inclusional materials. Boron (B), scandium (Sc), and yttrium (Y) may also be included.

[0257] One approach to eliminating the spontaneous and piezoelectric polarization effects in GaN or Ill-nitride based optoelectronic devices is to grow the Ill-nitride devices on nonpolar planes of the crystal. Such planes contain equal numbers of Ga (or group III atoms) and N atoms and are charge-neutral. Furthermore, subsequent nonpolar layers are equivalent to one another so the bulk crystal will not be polarized along the growth direction. Two such families of symmetry-equivalent nonpolar planes in GaN are the { 11-20} family, known collectively as a-planes, and the { 1- 100} family, known collectively as m-planes. Thus, nonpolar Ill-nitride is grown along a direction perpendicular to the (0001) c-axis of the Ill-nitride crystal. Another approach to reducing polarization effects in (Ga,Al,In,B,Sc,Y)N devices is to grow the devices on semi-polar planes of the crystal. The term “semi- polar plane” (also referred to as “semipolar plane”) can be used to refer to any plane that cannot be classified as c-plane, a-plane, or m-plane. In crystallographic terms, a semi-polar plane may include any plane that has at least two nonzero h, i, or k Miller indices and a nonzero 1 Miller index.

[0258] Some commonly observed examples of semi-polar planes include the (11-22), (10-11), and (10-13) planes. Other examples of semi-polar planes in the wurtzite crystal structure include, but are not limited to, (10-12), (20-21), and (10-14). The nitride crystal’s polarization vector lies neither within such planes or normal to such planes, but rather lies at some angle inclined relative to the plane’s surface normal.

[0259] For example, the (10-11) and (10-13) planes are at 62.98° and 32.06° to the c-plane, respectively.

[0260] The term “N-polar” refers to the (000-1) plane of Ill-nitride materials. References

[0261] The following references are incorporated by reference herein.

[0262] [1] U. K. Mishra, P. Parikh and Y.-F. Wu, "AlGaN / GaN HEMTs-an overview of device operation and applications," Proceedings of the IEEE, vol. 90, no. 6, pp. 1022-1031, 2002.

[0263] [2] S. P. DenBaars, D. Feezell, K. Kelchner, S. Pimputkar, C.-C. Pan, C.-C. Yen, S. Tanaka, Y. Zhao, N. Pfaff, R. Farrell, M. Iza, S. Keller, U. Mishra, J. S. Speck and S. Nakamura, "Development of gallium-nitride-based light-emitting diodes (LEDs) and laser diodes for energy-efficient lighting and displays," Acta Materialia, vol. 61, no. 3, pp. 945-951, 2013.

[0264] [3] U. K. Mishra, L. Shen, T. E. Kazior and Y.-F. Wu, "GaN-Based RF Power Devices and Amplifiers," Proceedings of the IEEE, vol. 96, no. 2, pp. 287-305, 2008.

[0265] [4] B. Romanczyk, S. Wienecke, M. Guidry, H. Li, E. Ahmadi, X. Zheng, S. Keller and U. K. Mishra, "Demonstration of Constant 8 W / mm Power Density at 10, 30, and 94 GHz in State-of-the-Art Millimeter- Wave N-Polar GaN MISHEMTs," IEEE Transactions on Electron Devices , vol. 65, no. 1, pp. 45- 50, 2018.

[0266] [5] W. Li, B. Romanczyk, E. Akso, M. Guidry, N. Hatui, C. Wurm, W. Liu, P.

[0267] Shrestha, H. Collins, C. Clymore, S. Keller and U. K. Mishra, "Record 94 GHz performance from N-polar GaN-on-Sapphire MIS-HEMTs: 5.8 W / mm and 38.5% PAE," in International Electron Devices Meeting (IEDM), San Francisco, CA, USA, 2022.

[0268] [6] B. Wang, K. Khan, E. Akso, H. Collins, T. Chavan, M. Guidry and U. Mishra, "Self-aligned Scaled Planar N-polar GaN HEMTs with Raised Regrowth," in Device Research Conference (DRCf College Park, MD, USA, 2024.

[0269] [7] B. Romanczyk, X. Zheng, M. Guidry, H. Li, N. Hatui, C. Wurm, A. Krishna, E. Ahmadi, S. Keller and U. K. Mishra, "W-Band Power Performance of SiN- Passivated N-Polar GaN Deep Recess HEMTs," IEEE Electron Device Letters, vol. 41, no. 3, pp. 349-352, 2020.

[0270] [8] N. Hatui, A. Krishna, H. Li, C. Gupta, B. Romanczyk, D. Acker-James, E.

[0271] Ahmadi, S. Keller and U. K. Mishra, "Ultra-high silicon doped N-polar GaN contact layers grown by metal-organic chemical vapor deposition," Semiconductor Science and Technology, vol. 35, no. 9, 2020.

[0272] [9] L. Lugani, M. Malinvemi, S. Tirelli, D. Marti, E. Giraud, J.-F. Carlin, C. R. Bolognesi and N. Grandjean, "n+-GaN grown by ammonia molecular beam epitaxy: Application to regrown contacts," Applied Physics Letters, vol. 105, no. 20, 2014.

[0273]

[0010] R. W. Johnson, A. Hultqvist and S. F. Bent, "A brief review of atomic layer deposition: from fundamentals to applications," Materials Today, vol. 17, no. 5, pp. 236-246, 2014.

[0274]

[0011] H.-Y. Shih, M.-C. Lin, L.-Y. Chen and M.-J. Chen, "Uniform GaN thin films grown on (100) silicon by remote plasma atomic layer deposition," Nanotechnology, vol. 26, no. 1, 2015.

[0275]

[0012] O. H. Kim, D. Kim and T. Anderson, "Atomic layer deposition of GaN using GaC13 and NH3," Journal of Vacuum Science & Technology A, vol. 27, no. 4, pp. 923-928, 2009.

[0013] F.-B. Ren, S.-C. Jiang, C.-H. Hsu, X.-Y Zhang, P. Gao, W.-Y. Wu, Y-J. Chiu, S.-Y. Lien and W.-Z. Zhu, "Deposition Mechanism and Properties of Plasma- Enhanced Atomic Layer Deposited Gallium Nitride Films with Different Substrate Temperatures," Molecules, vol. 27, no. 23, 2022.

[0276]

[0014] S. Banerjee, A. A. I. Aamink, D. J. Gravesteijn and A. Y. Kovalgin, "Thermal Atomic Layer Deposition of Poly crystalline Gallium Nitride," The Journal of Physical Chemistry , vol. 123, no. 37, pp. 23214-23225, 2019.

[0277]

[0015] F. Romo-Garcia, H. J. Higuera- Valenzuela, D. Cabrera-German, D. Berman- Mendoza, A. Ramos-Carrazco, O. E. Contreras and R. Garcia- Gutierrez, "Gallium nitride thin films by microwave plasma-assisted ALD," Optical Materials Express, vol. 9, no. 11, pp. 4187-4193, 2019.

[0278]

[0016] Z.-X. Zhang, S.-C. Jiang, W.-Y. Wu, P. Gao, L. Jiang, Y. Qiu, D.-S. Wuu, F.-M. Lai, S.-Y. Lien and W.-Z. Zhu, "Improved electrical contact property of Si- doped GaN thin films deposited by PEALD with various growth cycle ratio of SiNx and GaN," Surfaces and Interfaces, vol. 41, p. 103295, 2023.

[0279]

[0017] T. Zhu and R. A. Oliver, "Unintentional doping in GaN," Physical Chemistry Chemical Physics, vol. 14, pp. 9558-9573, 2012.

[0280]

[0018] Boyu Wang, William J. Mitchell, Chulong Wang, Robert Hamwey, Kamruzzaman Khan, Stacia Keller, Umesh K. Mishra; N-polar gallium nitride doping by atomic layer deposition for improved electrical performance. Appl. Phys. Lett. 2 June 2025; 126 (22): 222101.

[0019] P. Cantu, S. Keller, U. K. Mishra, S. P. DenBaars; Metalorganic chemical vapor deposition of highly conductive A10.65Ga0.35N films. Appl. Phys. Lett. 26 May 2003; 82 (21): 3683-3685.

[0281]

[0020] Keller, S., Lu, J., Mishra, U.K., DenBaars, S.P and Speck, J.S. (2012), Effect of indium on the conductivity of poly-crystalline GaN grown on high purity fused silica. Phys. Status Solidi A, 209: 431-433. bngs: / / doL& Kfl.0C2 / ^

[0282]

[0021] Sansaptak Dasgupta, Nidhi, David F. Brown, Feng Wu, Stacia Keller, James S. Speck, Umesh K. Mishra; Ultralow nonalloyed Ohmic contact resistance to self aligned N-polar GaN high electron mobility transistors by In(Ga)N regrowth. Appl. Phys. Lett. 5 April 2010; 96 (14): 143504.

[0022] https: / / plasma.oxinst.com / products / ald / flexal-ald Conclusion

[0283] This concludes the description of the preferred embodiment of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the clauses appended hereto.

Claims

WHAT IS CLAIMED IS:

1. A device comprising: one or more III-Nitride semiconductor layers, as characterized by deposition using atomic layer deposition, comprising n-type or p-type dopants with a dopant concentration of at least 1.3E18 cm’3and a carrier mobility of at least 7 cm2 / V-s.

2. The device of claim 1, wherein the dopants occupy empty spots or vacancies left by one or more Group-Ill precursor doses in the Ill-nitride semiconductor layers and / or form a separate layer on the layer of Group III element or on or between the III-Nitride layers, wherein a number of the empty spots or vacancies is process adjustable to modify electrical performance including the mobility.

3. The device of claim 1, wherein the dopants comprise indium, silicon, oxygen, germanium, sulfur, magnesium, zinc, beryllium or an indium containing compound layer alone or in combination with at least one other co-dopant.

4. The device of claim 1, wherein the III-Nitride layers comprise an N- polar or metal-polar or semipolar or nonpolar III-Nitride semiconducting layer.

5. The device of claim 1, wherein one or more of the III-Nitride semiconductor layers have a resistivity of no more than 0. 6 ohm cm6. The device of claim 1, wherein the layers have atomically sharp interfaces and comprise one or more monolayers each comprising group III atoms, nitrogen atoms, or a combination of both.

7. The device of claim 1, wherein the III-Nitride layers are conformal with an underlying surface comprising: inside and outside portions of a trench having an aspect ratio (height to width ratio) of at least 2 or a horizontal surface and a sidewall having an angle in a range of 0.1-90 degrees with respect to the horizontal surface.

8. The device of claim 1, further comprising a contact layer comprising the III-Nitride semiconductor layers.

9. The device of claim 8, wherein the dopant concentration forms an ohmic contact with a metal layer.

10. The device of claim 8, further comprising an active region, further comprising the contact layer between a metal layer and the active region, wherein the contact layer in contact having flat top surface and inclined sidewall conformal with the underlayer.

11. The device of claim 1, wherein at least one of the III-Nitride semiconductor layers comprises a sub -saturation dose of Group III precursor tailored for the dopant concentration.

12. A method of fabricating a device, comprising: depositing one or more III-Nitride semiconductor layers using atomic layer deposition in a presence of dopants under conditions to form the one or more III- Nitride semiconductor layers having a dopant concentration of at least 1.3E18 cm-3 and a carrier mobility of at least 7 cm2 / V-s.

13. The method of claim 12, wherein the depositing comprises forming at least one of the layers using a sub-saturation dose of Group III precursor dose tailored for the dopant concentration; and exposing the one or more layers having the sub-saturation dose to the n-type or p-type dopants.

14. The method of claim 13, wherein the dopants fill empty spots or vacancies formed in the layer with the sub-saturation dose, or and / or the dopants form a separate layer on the layer of Group III element or on or between the III-Nitride semiconductor layers.

15. The method of claim 12, wherein the III-Nitride semiconductor layers comprise an N-polar, semipolar, metal-polar, or nonpolar III-Nitride semiconducting layer.

16. The method of claim 12, wherein the depositing comprises:(a) loading a substrate in a plasma enhanced ALD reactor;(b) exposing a surface of the substrate to a group III material containing precursor using a saturated or sub-saturated dose to form a first layer on the surface;(c) purging the reactor of the group III material containing precursor;(d) exposing the first layer to a first plasma comprising a nitrogen containing gas or a nitrogen-containing gas without plasma to form the III-Nitride semiconductor layer;(e) purging the reactor; exposure to a dopant precursor, comprising at least one of: providing the dopant precursor together with the group III material precursor in step (b) or after the purging step (c) but prior to step (d) to form the first layer, wherein the step optionally further comprises a purge of the dopant precursor immediately after exposure of the dose of the dopant precursor; orproviding the dopant precursor after the step (d) but prior to the purging step(e), or providing the dopant precursor after the step (e)17. The method of claim 16, further comprising a second plasma step after step (d) and prior to step (e)18. The method of claim 16, wherein the temperature of the substrate during steps (b)-(e) is less than 500 degrees Celsius, the power of the plasma is above a first threshold level and a pressure in the reactor during steps (b)-(e) is below a second threshold level such that the III-Nitride semiconducting layer has a resistivity of no more than 0.6 ohm cm and a surface RMS roughness of no more than 10 nm over an area of 10 microns by 10 microns.

19. The method of claim 16, wherein the group III precursor dosed for at least 1 microsecond, the first plasma comprises the nitrogen containing gas comprising ammonia and / or ammonia / nitrogen, and / or ammonia / hydrogen, and / or nitrogen, and / or nitrogen / hydrogen, the second plasma comprises nitrogen and / or argon, and the purging is with a gas comprising nitrogen and / or argon, the power is at least 1 W and up to 1E4 W, and the pressure is below 760 Torr.

20. The method of claim 16, further comprising: depositing one or multiple cycles of steps (b)-(e) prior to exposure to a dopant cycle comprising the dopant precursor (including saturation or sub -saturation doses) followed by exposure to a plasma comprising a nitrogen containing gas.

21. The method of claim 16, wherein the carrier gas for any of the precursors comprises at least one of hydrogen, nitrogen, or argon, and the purging gas comprises at least one of nitrogen or argon.

22. The method of claim 12 , further comprising annealing the III-Nitride layer to control or modify the conductivity of the III-Nitride semiconductor layers.

23. The method of claim 22, where the conductivity is modified locally, by local treatment of the III-Nitride semiconductor layers with a laser or an electron beam.

24. The method of claim 16, comprising a plurality of cycles of the steps (b)-(e), wherein one or more of the steps (b) comprise a sub -saturation dose of the group-III precursor and / or dopant precursor.

25. The method of claim 24, wherein the sub -saturation dose is followed by the dopant precursor dose to increase dopant incorporation every time or after a pre-defined number of the cycles with a saturation dose of the group III precursor.

26. The method of claim 12, wherein the III-Nitride semiconductor layers comprise a GaN layer and the method further comprises: depositing a dielectric deposited by ALD on the GaN layer, or a metal layer deposited by ALD on the GaN layer, , e.g. ALD ruthenium, platinum, or aluminum.

27. The method of claim 12, wherein the III-Nitride semiconductor layers comprise a doped layer on an unintentionally doped layer and / or wherein a thin layer (0-5 nm) of unintentionally doped Ill-nitride layer added before or after any doping layers.

28. The method of claim 12, further comprising performing a plasmacleaning step before the atomic layer deposition.

29. The method of claim 12, wherein: the layers are grown on either homogenous or heterogeneous surfaces including but not limited to Ill-nitride semiconductor layers, metal, and dielectric, and / or layers are on co-existing or contiguous planes of different orientations, for example, samples with patterned surfaces, of varying or similar polarizations in sign and magnitude or non-polar planes.

30. The method of claim 12, wherein Indium is added during the ALD growth (at any steps) via Indium precursor doses, or after the growth via diffusion or implantation.

Images