Growth of AlxGa1-xAs, Al0.5In0.5P, and AlxGa(0.5-x)In0.5P by hydride vapor phase epitaxy using an external AlCl3 generator

Abstract

Herein, Al by hydride vapor phase epitaxy (HVPE) using an external AlCl generator x Ga 1-x As, Al x In 1-x P, and Al x Ga y In 1-x-y Controlled epitaxy of P is disclosed.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 62 / 910,923, filed October 4, 2019, the entire contents of which are incorporated herein by reference.

[0002] The United States Government has rights in this invention under Contract No. DE-AC36-08GO28308 between the United States Department of Energy and the Alliance for Sustainable Energy, LLC (which manages and operates the National Renewable Energy Laboratory). [Background technology]

[0003] Al-containing arsenide and phosphide materials are essential to the performance of many III-V optoelectronic devices. Substitution of Al for Ga in GaAs and GaInP leads to a large increase in the bandgap, but with only minimal changes in the lattice constant, making the knob for tuning the bandgap nearly irrelevant. This property enables the rapid formation of high-quality heterobarriers that are essential to the performance of optoelectronic devices such as transistors, light-emitting diodes, and photovoltaics. Al-containing compounds can also function as wide bandgap active regions in optoelectronic devices, with the Al solid content providing direct control of the device bandgap.

[0004] Hydride vapor phase epitaxy (HVPE) is an epitaxial growth method that has the potential to reduce epitaxial growth costs for III-V optoelectronics. HVPE predates the development of metalorganic vapor phase epitaxy (MOVPE), the primary III-V growth technique used in current manufacturing. Throughout the 1970s and 1980s, commercial production of light-emitting diodes and photodetectors and emitters for the telecommunications industry was achieved using HVPE. HVPE was considered the best choice for producing materials with exceptional purity and electronic quality, but in the 1980s it began to fall out of favor over MOVPE for two main reasons. First, while MOVPE readily allows for the formation of extremely abrupt heterointerfaces, HVPE has historically suffered from heterointerfaces due to the process inertia associated with the high growth rates and in situ generation of group III precursors. The second is the well-known difficulty in adhering Al-containing materials in HVPE, another growth aspect that is superior in MOVPE.

[0005] Aluminum monochloride (AlCl), similar to the commonly used HVPE precursors GaCl and InCl, is highly unstable and corrodes quartz, requiring an alumina or graphite component. To further complicate matters, attempts to grow Al-containing compounds from AlCl have required growth temperatures of up to 1000 °C to suppress pre-deposition. The large thermodynamic differences between the growth of GaAs and AlAs mean that the growth of Al from GaCl and AlCl is difficult. x Ga 1-x The formation of As alloys was prevented and only binary phases were formed. eq suggested a large driving force for depositing this material, which would be difficult to control at more conventional growth temperatures. Finally, the researchers did indeed demonstrate that Al grown by HVPE x Ga 1-xAlthough As has been demonstrated, it was only by using a mixed Ga / Al source, which is not conducive to commercial production due to the difference in the depletion rates of Al and Ga in the melt leading to a floating solid composition. These difficulties have been the main reasons why MOVPE has become the dominant technology for III-V optoelectronic device production.

[0006] However, aluminum monochloride is not the only possible Al-containing HVPE precursor. Aluminum trichloride, AlCl3, is much more stable than AlCl and does not readily react to form AlAs, as evidenced by the negligible equilibrium constant for the deposition of AlAs from AlCl3. Despite the low driving forces for direct solid-state deposition from AlCl3, various reports published in the late 1980s and early 1990s have demonstrated the synthesis of AlAs and Al by HVPE. x Ga 1-x We demonstrate that growth of As is possible at a comparably low temperature of 500 °C using AlCl3. Again, such results were achieved through a kinetically controlled growth pathway.

[0007] AlCl3 is solid below about 195°C and has a low vapor pressure at room temperature. Thus, some groups have used this embodiment, but it requires a heating source and processing line to transport this precursor using an inert carrier. However, this method is limited in the molar flow rate that can be delivered at standard line temperatures and bubbler flows. An alternative method is to generate AlCl3 from solid Al and HCl. Thermodynamic calculations indicate that the formation of AlCl3 is favored over AlCl at temperatures below about 700°C, with AlCl3 selectivity increasing as the temperature of the Al source is decreased. These same predictions suggest that AlCl3 may decompose to AlCl+HCl when it reaches the hot section of the downstream reactor, which can create problems associated with reactive monochlorides. However, high temperature (<1000°C) Al-nitride growth has demonstrated that the AlCl3 molecule is not susceptible to decomposition after generation. The generation of AlCl3 can be achieved in situ or externally, allowing for greater flexibility in the design of the quartz reactor.

[0008] A long-standing problem with LPE relates to the growth of Al-containing III-V alloys that are interesting for optoelectronics, especially visible LEDs. With the notable exception of AlGaAs, many Al-containing III-V alloys (such as AlInP and AlGaInP) are notoriously difficult to grow by LPE. This is ironic, since one of the original and most compelling motivations for developing LPE was historically related to the ability to grow AlGaAs structures, which were less susceptible to oxidation effects in LPE than by CVD. Previously, it was nearly impossible to grow AlGaInP alloys either by LPE or chloride VPE. More generally, before the development of MOCVD and the use of metalorganic precursors for Al, the high affinity of Al compounds for oxygen made vapor phase growth of Al-containing III-V materials infeasible. For LPE of AlGaInP, the difficulty was related to the controlled incorporation of Al into the solidified III-V epilayer. Specifically, the phase equilibrium calculations assume that the growth of AlGaInP from an Al-In-Ga-P melt (or the growth of AlInP from an Al-In-P melt) occurs as a dilute solution in aluminum (X Al ≒10-4), indicating that an indium-rich melt composition is required. However, the high segregation coefficient (k Al ≈104–105) means that the melt rapidly consumes aluminum and the Al fraction in the epilayer changes dramatically.

[0009] The inadequacy of segregation control to achieve target compositional profiles of ternary and quaternary layers is a significant drawback of LPE. This problem appears to be an intrinsic limitation of LPE, since, to begin with, the composition of the LPE layer is determined by phase equilibrium considerations.

[0010] Previous work has used short growth times from equilibrium solutions with high aluminum fractions and Al 0.9 Ga 0.1By growing AlGaInP on an As buffer layer, we have achieved AlInGaP grown by LPE with high Al content. We measured the AlGaInP electroluminescence emission wavelength of 645 nm, which is outside the 590-630 nm range of commercially available ultra-bright AlGaInP LEDs, but suggests that improvement in the aluminum segregation phenomenon in Al / In-containing III-V alloys is possible.

[0011] In general, the compositional grading observed in LPE is due to two effects: depletion of the components from the melt above, and changes in temperature-dependent segregation as the melt cools. High segregation coefficients (e.g., k>10) exacerbate the melt depletion effect. More complex melt compositions can be considered that include "neutral" components such as bismuth, tin, lead, and other elements that are incorporated in the epitaxial layers in very small amounts but may modify the segregation coefficients of the epilayer components.

[0012] It is therefore conceivable that melt compositions and additions to the melt can be tailored to increase or decrease the liquid phase activity coefficients of certain components, thereby increasing or decreasing their segregation coefficients. In particular, "neutral solvents" such as Pb and Bi in III-V LPE can be studied for their effect on segregation. The supersaturation dependence of the segregation coefficient in solution growth can also be manipulated in LPE. The temperature effect on segregation can be improved using solid sources, imposing temperature differences, or steady-state methods of growth driven by current-induced electromigration or the Peltier effect. In general, it is uncertain whether the segregation coefficients of chemical species can be altered by factors of 10 or even 100 by optimizing the melt composition.

[0013] The segregation of the components can be tailored by applying an electric current across the growth interface, such as the expression derived for the (dopant) segregation change in LPEE of the LPEE growth parameters. Presumably, the segregation of alloy components (e.g., Al) in addition to dopants can be altered by applying an electric current as well. Furthermore, the use of an AlGaAs (or AlGaP) solid source in contact with the melt during growth can be used to replenish the melt with Al rather than using a GaAs (or GaP) source or relying on an As-saturated Al-containing melt, thereby reducing the compositional gradient due to Al depletion from the melt. A similar approach has been used with solution growth of bulk GaInSb crystals, where polycrystalline GaInSb is used for the continuous solute supply of the growth solution. In the case of Al segregation in Al-containing III-V alloys, predictions of the extent of segregation that can be altered by electroepitaxy effects or tailored melt composition have shown that these approaches are reasonably useful, but melt compositions that can dramatically affect aluminum segregation have not been fully explored. Aluminum segregation during AlGaAs LPE occurs due to the ultrafast cooling rate (102-103℃s -1 ) can be used, the aluminum composition grading in the epilayer can be opposite to that observed in slow-cooling LPE.

[0014] Another option is to grow thin layers of alloy semiconductors in successive LPE steps. In the case of aluminum III-V alloys, multiple thin layers of high Al content alloys can be grown from separate melts, followed by post-growth annealing to homogenize the compositional profile. Finally, certain growth techniques to control segregation developed for bulk crystal growth of ternary alloys are adaptable to LPE. For example, the double crucible method, the floating crucible method or the solute feeding method (controlled delivery of solute to the growth interface by diffusion through one or more capillaries connecting two melts of specific composition) are feasible for LPE. Summary of the Invention [Problem to be solved by the invention]

[0015] In general, the application of LPE for the growth of heterostructures with relatively large lattice mismatches is difficult to prove. Typically, LPE has been limited to the growth of epitaxial layers with less than 1% relative lattice mismatch between the epitaxial layer and the substrate, although there are many exceptions, as discussed below. In many cases, it is difficult or problematic to induce a thermodynamic driving force to grow from the liquid phase sufficient to overcome the energy barrier associated with nucleating a lattice-mismatched epilayer on a substrate. The required high supersaturation can lead to homogeneous nucleation in the bulk of the melt. Even if homogeneous nucleation can be avoided, high supersaturation promotes three-dimensional separate nucleation and coalescence of separate nuclei to form a continuous layer, resulting in defects. Also, in many heterostructure pairs, there is a large disparity between the melt and the exposed solid phase (i.e., the substrate or the epilayer grown in the previous step), and thus contact with the melt results in distinct dissolution of the underlying substrate or epilayer. As a specific example, to grow InGaP on GaAs, a GaAs substrate is contacted with a melt containing In, Ga, and P. This melt cannot come into equilibrium with the GaAs substrate and will tend to melt back the substrate to saturate the melt with arsenic, and the regrowth will be InGaAsP. The limitations associated with the growth of heterostructures are one of the main drawbacks of LPE techniques over MBE and MOCVD. [Means for solving the problem]

[0016] Thus, LPE of heterostructures has raised many problems, many of which were related to phenomena that narrow the scope of LPE or limit the abruptness of the interface for producing multiple heterostructure types. It is almost inevitable that the interface between the melt and the substrate (or previously grown layers) will exhibit thermodynamic instabilities, resulting in potential dissolution (etch-back) of the substrate and thus changing the melt composition around the substrate. Fortunately, there are many systems in which GaAs-bearing AlGaAs, InGaP-bearing GaAs, and InP-bearing InGaAs dissolution can be avoided or minimized. In many cases, increasing the degree of supersaturation can suppress substrate melt-back. Melt-back has been reduced in GaInAsP / InP LPE heteroepitaxy using lattice surfaces, Sn-based melts, and low growth temperatures. It has been demonstrated that the addition of Se to the melt can prevent substrate melt-back during InP-bearing GaAs LPE. The complex phenomena occurring during LPE heteroepitaxy, such as dissolution of the substrate, solid-phase diffusion of substrate components and liquid-phase diffusion of melt components, formation of dislocation layers, achievement of local equilibrium and lattice mismatch effects, have been demonstrated.

[0017] In one aspect, disclosed herein is a method for depositing Al-containing III-V materials by hydride vapor phase epitaxy (HVPE) using an external AlCl generator. In one embodiment, the source temperature of the external AlCl generator is about 400 degrees Celsius. In one embodiment, the AlCl molecules do not decompose during the deposition process. In one embodiment, the deposition temperature is in the range of 620-700 degrees Celsius. In one embodiment, the Al-containing III-V materials are deposited using Al x Ga 1-x As, where x is 0-1. In some embodiments, the Al-containing III-V material has a V / III ratio of 10-300. In some embodiments, the group V species is selected from the group consisting of nitrogen, phosphorus, arsenic, and antimony. In some embodiments, the method further comprises using AsH3.

[0018] In one embodiment, lattice-matched AlCl is prepared by using an external AlCl generator. x In 1-xP and Al x Ga y In 1-x-y Disclosed herein is a method for HVPE deposition of P, where x varies from 0 to 1. In an embodiment, the source temperature of the external AlCl3 generator is about 400 degrees Celsius. In an embodiment, the AlCl3 molecule does not decompose during the deposition process. In an embodiment, the deposition temperature is in the range of 620-700 degrees Celsius. In an embodiment, the V / III ratio of the Al-containing III-V material is 10-300. In an embodiment, the group V species is selected from the group consisting of nitrogen, phosphorus, arsenic, and antimony. In an embodiment, the method further comprises the use of AsH3.

[0019] In an aspect, disclosed herein is an optoelectronic device fabricated using a method of depositing Al-containing III-V material by HVPE using an external AlCl3 generator. In an embodiment, the optoelectronic device is fabricated by a method in which the source temperature of the external AlCl3 generator is about 400 degrees Celsius. In an embodiment, the optoelectronic device is fabricated by a method in which the AlCl3 molecule does not decompose during the deposition process. In an embodiment, the optoelectronic device is fabricated by a method in which the deposition temperature is in the range of 620-700 degrees Celsius. In an embodiment, the optoelectronic device is fabricated by a method in which the Al-containing III-V material is lattice-matched Al x In 1-x P and Al x Ga y In 1-x-y It is produced by a process including P.

[0020] The exemplary embodiments of the invention disclosed herein demonstrate a method for controlled deposition of Al-containing III-V materials by HVPE using an external AlCl3 generator. The generation of AlCl3 relative to AlCl was selected to use a source temperature of 400°C, allowing reliable control of the solid Al composition. The AlCl3 molecule was not susceptible to decomposition at typical source and deposition temperatures in the reactor. Al x Ga 1-x As solid composition and Al x Ga 1-xThe effects of growth conditions such as deposition temperature, V / III ratio, and group V species on As growth rate were elucidated. Conditions that preferentially select AsH3 over As2 / As4 were found to strongly promote the incorporation of Al in the thin films. Al = Al in the full range from 0 to 1 x Ga 1-x Control of As composition and nearly lattice-matched Al x In 1-x P and Al x Ga y In 1-x-y The growth of P has been achieved by HVPE for the first time. These results have implications for the growth of novel high-performance optoelectronic devices by HVPE.

[0021] Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. [Brief description of the drawings]

[0022] [Figure 1] 1 shows a graph of the equilibrium constants for deposition of solid AlAs and GaAs using various group III precursors and As vapor (As4) or As hydride (AsH3). [Diagram 2] 1 shows a diagram (not to scale) of an embodiment of an HVPE reactor vessel used in the methods disclosed herein, including an external AlCl 3 generator. [Diagram 3] Figure 1 shows the growth rate (right) and growth rate (left) of AlxGa1-xAs as a function of H2 carrier flow rate to the external Al boat. The HCl flow rate to the boat and all other growth conditions were kept constant. [Figure 4] Figure 1 shows the xAl (left) and growth rate (right) of AlxGa1-xAs epilayers grown with constant source temperature (TD) and varying (Ts), while all other growth parameters were kept constant. [Diagram 5] The xAl (left) and growth rate (right) of AlxGa1-xAs epilayers grown with varying deposition temperature (TD) at constant source temperature (Ts). [Figure 6] Figure 1. Growth rates of AlxAl (left) and AlxGa1-xAs (right) as a function of AsH3 flow rate for epilayers grown at TD = 650 °C, all other parameters held constant. [Figure 7] Figure 1. Growth rates of AlxAl (left) and AlxGa1-xAs (right) as a function of AsH3 carrier flow rate for epilayers grown at TD = 650 °C, all other parameters held constant. [Figure 8] Figure 1 shows (004) omega-2theta HRXRD scans of AlxGa1-xAs epilayers spanning nearly the entire compositional space. [Figure 9a-9b] 9 shows the transmission spectra of an AlxIn1-xP epilayer in FIG. 9a and an AlxGayIn1-x-yP epilayer in FIG. 9b bonded to glass. [Figure 10] Assuming complete conversion of HCl to MClx, we show xAl in AlxIn1-xP epilayers grown nearly lattice matched to GaAs as a function of the InCl / AlCl3 ratio. [Figure 11a-11b] 1 shows X-ray (004) scans and Nomarski images of lattice-matched AlInP grown by HVPE using the method and reactor disclosed herein. Figure 11a shows a (004) omega-2 theta XRD scan of an Al0.53In0.47P epilayer. Figure 11b shows Nomarski microscope images (20x) of Al0.53In0.47P with different Al contents. [Figure 12] The internal quantum efficiency of AlGaAs passivated single-junction GaAs solar cells at various wavelengths of light is shown in Figure 12. Two vertical GaAs devices passivated with Ga0.5In0.5P and Al0.4Ga0.6As achieved similar quantum efficiencies, indicating that AlGaAs grown at a low temperature of 650°C (the growth temperature is also conducive to the growth of GaInP) provides effective passivation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Prior to the use of the methods and devices disclosed herein, it was believed that quaternary alloy AlGaInP materials could not be grown by conventional mass production growth processes such as liquid phase epitaxy (LPE) and hydride vapor phase epitaxy (VPE). The difference in the thermodynamic stability of aluminum phosphide (AIP) and indium phosphide (InP) makes composition control very difficult by LPE. Furthermore, the problem of forming stable aluminum chloride (AlCl) compounds during hydride or chloride vapor phase epitaxy prevented the successful growth of Al-containing phosphides by VPE.

[0024] In this specification, Al by HVPE using an external AlCl3 generator x Ga 1-x As, Al x In 1-x P, and Al x Ga y In 1-x-y A method and device for controlled epitaxy of P is disclosed. Limiting the Al source temperature to 400° C. promoted the formation of AlCl3 instead of AlCl (AlCl is a precursor that prevents controlled deposition of multi-element Al-containing compounds and is reactive with the quartz reactor). The conversion of HCl to AlCl3 in the source zone was shown to reach a maximum at this temperature. The deposition temperature, V / III ratio, and Al x Ga 1-x The effects of As-loaded group V precursor solid composition and growth rate were determined. The presence of AsH3 at the growth surface was found to be effective in kinetically promoting the incorporation of Al into the growing film. x Ga 1-x Controlled deposition of As was demonstrated, and for the first time, Al by HVPE. x In 1-x P and Al x Ga y In 1-x-y It has been demonstrated that the growth of P is possible. Using the methods and devices disclosed herein, the deposition by HVPE of novel heterobarrier optoelectronic devices with Al-containing layers has been demonstrated, a result not previously achievable.

[0025] In this specification, external AlCl x A method and device for depositing Al-containing III-V compounds by HVPE using a generator is disclosed. AlCl3 generation is performed using a source temperature of 400°C and a X Al = Al ranging from 0 to 1 x Ga 1-x The AlCl3 molecule was chosen to allow for controlled deposition of the entire compositional range of As. It was verified that the AlCl3 molecule is not susceptible to decomposition in the typical temperature range used in our reactor. The growth conditions, such as growth temperature, V / III ratio, and group V species, were chosen to allow for controlled deposition of the entire compositional range of X, Y, and As. Al and Al x Ga 1-x The effect of As on the As growth rate was evaluated. The condition of AsH3 over As2 / As4 strongly promotes Al incorporation. x In 1-x P and Al x Ga y In 1-x-y The growth of P is demonstrated for the first time by HVPE, overcoming the problems with the AlCl precursor that previously hindered its growth. These results show that controlled deposition of Al-containing arsenides and phosphides is possible with HVPE, in contrast to what was previously taught in the art.

[0026] First, a series of Al x Ga 1-x As sample is T D = 650°C growth, HCl->AlCl in Al boat at 400°C x The conversion efficiency was tested by varying the H2 carrier flow rate, H2(Al), to an Al boat with a constant HCl(Al) flow rate, all other growth conditions held constant. This experiment tests the conversion efficiency by varying the residence time of the HCl in the boat. At 400 °C, thermodynamic calculations indicate that when the system is allowed to reach equilibrium, nearly 100% of the input HCl is converted to AlCl xHowever, if the residence time of HCl relative to Al in the boat is not long enough, as is commonly observed for Ga sources, kinetic limitations prevent the system from reaching equilibrium. By increasing the H2 carrier flow rate at a constant HCl flow rate, one can decrease the residence time in the boat and observe how the incorporation of Al in the solid is affected.

[0027] Figure 3 shows the Al solids content (left) and growth rate (right) for this series of samples. First, as the H2(Al) flow rate is increased from 75 to 300 sccm, the X Al X increases slightly from 0.58 to 0.61, while the growth rate increases from 5 to 7 μm / h. Although the specific cause of these trends is unknown, these results are the opposite of what would be predicted if HCl conversion was incomplete, suggesting that this parameter is not growth limiting. Above 300 sccm H2(Al), the growth rate and X Al The amount of AlCl in the solids is reduced, indicating that the residence time of HCl in the boat is too short, and the source conversion reaction no longer reaches completion. Al This, together with the increased concentration of unreacted HCl in the reaction vessel, suppresses the growth rate. Al Note that the high HCl(Al) / HCl(Ga) ratios required to achieve K = 0.5-0.6 (assuming complete conversion of all HCl to AlCl3 and GaCl) suggest that the species reaching the substrate surface is AlCl3, as opposed to the highly reactive AlCl as shown in Figure 1. Figure 1 shows the equilibrium constants, K, for the growth of GaAs and AlAs from different group III precursors and a) As4 or b) AsH3, calculated from thermodynamic data. eq These calculations do not include equilibria between other gas phase precursors.

[0028] Next, we confirmed whether AlCl3 generated in the Al source decomposed into AlCl and HCl before reaching the substrate. S Changing T DIt is a useful method for changing the chemistry in a reaction vessel without changing the reactant flow. S was varied to affect the decomposition of AsH3 in the reactor, independent of other growth parameters. Figure 4 shows the results of a similar experiment, but with T S is a constant T D This is the AlCl in the reaction vessel under a constant reactant flow of x Determine whether the distribution of chemical species changes. Al is T S It is nearly constant when T varies between 650 and 800 °C. The growth rate is also nearly constant until it shows a decrease at T = 800 °C. The decomposition of AsH3 may increase at this temperature, which may decrease the growth rate. The Al solids content and growth rate are almost constant when T S The fact that it is less susceptible to X Al Combined with the high HCl(Al) / HCl(Ga) required to obtain compositions above >0.50, this strongly suggests that the Al growth species in the reaction vessel is AlCl3 and does not substantially decompose to AlCl.

[0029] AlCl3 to Al by HVPE x Ga 1-x Experiments were carried out to understand the growth parameter space for growing As. Figure 5 shows the effect of deposition temperature at constant HCl(Al) flow. Al is T D The growth rate increases significantly with T, but the growth rate changes slightly and reaches a maximum at 650°C. D X increases with Al The trend of T coincides with the equilibrium curve in Fig. 1, which indicates that the driving force for the growth of AlAs from AlCl3 is T D We predict that the driving force for the growth of GaAs from GaCl increases with increasing K eqThe growth rate is relatively insensitive within this temperature range, due to these opposing trends in. This result further suggests that AlCl3 is the primary Al precursor in the reaction vessel, since growth from AlCl and GaCl is expected to show a monotonic growth rate decrease based on Figure 1.

[0030] Flow rate and nature of V-group precursor Al x Ga 1-x The effect of AsH3 flow rate on the growth of X Al Without being bound by theory, the effect of AsH3 flow rate on the growth rate is shown in Fig. 1. As the AsH3 flow rate increases from 45 to 100 sccm, the Al The growth rate doubles within this range, and X increases slightly with respect to this parameter. Al The results show that increased AsH flow rates increase the incorporation of both Ga and Al in the solid, because the relative influx of Ga is relatively insensitive to the AsH flow rates. x Ga 1-x has a very strong effect on As growth. GaAs growth rate can be enhanced by limiting the decomposition of the AsH3 precursor to As2 / As4. In that case, AsH3 decomposition is limited by increasing the flow rate of the H2 carrier input along with the AsH3, thereby increasing the velocity of AsH3 through the reactor and reducing its residence time in the 800°C source zone.

[0031] Figure 7 shows a series of Al grown with varying AsH3 carrier flow rates. x Ga 1-x As sample X Al and growth rate. Note that the H2 flow rate was compensated at a separate reactor port to ensure that the total H2 flow rate and reactant dilution level in the reactor was constant. Al increases significantly with the AsH3 carrier flow rate, and the growth rate also increases. These results indicate that the presence of crack-free AsH3 is important for the incorporation of Al. This is due to the K eqis extremely low, while K for the growth of AlAs from AlCl3 and AsH3 is eq is almost five orders of magnitude larger. However, K for the growth of AlAs from AlCl3 and AsH3 eq It is further noted that the equilibrium calculations do not tell the whole story, as the equilibrium calculations are still incomplete at 650 °C. The presence of unreacted AsH3 appears to modify the reaction kinetics at the substrate surface. AsH3 can provide reactive H groups that help drive the kinetic reduction of the otherwise highly stable AlCl3 molecules, aiding in the consumption of surface AlCl3 and explaining the trends observed in Figure 7.

[0032] External Al generators allow for controlled deposition of Al-containing compounds by HVPE. All these different growth trends taken together, X Al = 0 to 1 in the composition space x Ga 1-x Figure 8 shows the (004) X-ray diffraction curves for samples with Al contents varying from 0.11 to 0.93. The Al generator also enables the deposition of Al-phosphide compounds by HVPE, which has not been demonstrated by this growth technique so far.

[0033] Figure 9 shows (a) Al, which has a lattice matching composition close to GaAs. x In 1-x P and (b) Al x Ga y In 1-x-y Transmission measurements of the P epilayer are shown. These wide bandgap materials are useful in many III-V devices. For example, they can be easily integrated into devices such as solar cells to provide transparent passivation on the front and back sides, or they can be the active layer in an LED device emitting green wavelengths.

[0034] Figure 10 shows the near lattice-matched composition of AlCl3 / InCl grown as a function of the AlCl3 / InCl ratio. x In 1-x X of P epilayer Al Shows Al x Ga1-x For As growth, a small AlCl3 / InCl ratio is preferred to achieve a 50 / 50 solid composition, while Al x In 1-x We show that the growth of P can be controlled by using an AlCl precursor. The growth of these phosphide materials, as disclosed herein, will enable, for the first time, new, more efficient devices to be grown by HVPE. EXAMPLES

[0035] experiment Materials were grown in a dual chamber HVPE reactor at atmospheric pressure, as shown in Figure 2. Except where specified, GaCl and InCl were generated in situ from HCl and elemental Ga and In in hot zones 1 and 2 at a temperature of 800 °C. The substrate was (100) oriented GaAs with a 6° offcut towards the (111)A face. AlCl3 was generated outside the reactor in a separate quartz boat sealed inside a clamshell furnace. The temperature of the Al furnace was 400 °C to promote the generation of AlCl3 over AlCl. The generation of the Al precursor was controlled by the flow rates of HCl and H2 carrier to the boat, as shown in Figure 2. The process lines delivering the Al precursor to the reactor were heated to 200 °C using insulated freeze-out zones to prevent solidification of AlCl3 and subsequent blockage of the lines. The Al lines were plumbed to the reactor through an alumina tube extending through most of the upper source zone at 800 °C. The alumina tube is inert to reaction with AlCl3 or decomposition by-products, has an inner diameter of 4 mm, and facilitates high velocities through the hot source zone.

[0036] GaAs / Al x Ga 1-x The As / GaAs structure was grown, and the Al solid and Al x Ga 1-x The As growth rate was analyzed. The deposition temperatures (T D ) was 650 °C unless otherwise specified. AsH3 was the group V precursor. Al x Ga 1-xThe As lattice constant was measured using high-resolution X-ray diffraction on the (004) surface, and this was used to calculate the X Al The epilayer thickness and growth rate were determined by fitting the reflectivity of the sample using the transfer matrix method, and the n and k data were calculated. x In 1-x P and Al x Ga y In 1-x-y P epilayers were also grown from AlCl3, InCl, GaCl, and PH3 at a temperature of 650 °C. The quaternary compositions were determined through measurement of the lattice constants by X-ray diffraction and determination of the band gap by spectroscopic transmission measurements. The epilayers were bonded to glass handles with transparent epoxy, and transmission samples were prepared by selectively etching away the absorbing substrate using an ammonium hydroxide / hydrogen peroxide based etchant.

[0037] Using the methods and devices disclosed herein, we have demonstrated how to perform controlled deposition of Al-containing III-V materials by HVPE using an external AlCl3 generator. The generation of AlCl3 relative to AlCl was selected using a source temperature of 400°C, allowing reliable control of the solid Al composition. The AlCl3 molecule was shown to be not susceptible to decomposition at typical source and deposition temperatures in the reactor used herein. Growth conditions such as deposition temperature, V / III ratio, and group V species can be used to determine the amount of Al x Ga 1-x As solid composition and Al x Ga 1-x The effect of As on the As growth rate was determined. It was found that the selection of conditions for AsH3 over As2 / As4 strongly promoted the incorporation of Al into the thin film. Al = Al in the full range from 0 to 1 x Ga 1-x As composition and nearly lattice-matched Al x In 1-x P and Al x Ga y In 1-x-yControl over the growth of P has been achieved by HVPE for the first time. These results enable the growth of novel high performance optoelectronic devices by HVPE.

[0038] The foregoing disclosure has been presented merely to illustrate the present invention and is not intended to be limiting. The inventions described in the original claims of this application are listed below. [Invention 1] External AlCl 3 A method for depositing Al-containing III-V materials by hydride vapor phase epitaxy (HVPE) using a generator. [Invention 2] External AlCl 3 2. The method of claim 1, wherein the source temperature of the generator is about 400 degrees Celsius. [Invention 3] AlCl 3 2. The method according to claim 1, wherein the molecule does not decompose during the deposition process. [Invention 4] The method according to claim 1, wherein the deposition temperature is in the range of 620 to 700 degrees Celsius. [Invention 5] The Al-containing III-V material is Al x Ga 1-x 2. The method according to claim 1, comprising: [Invention 6] 6. The method according to claim 5, wherein the V / III ratio of the Al-containing III-V material is 10-300. [Invention 7] 2. The method of claim 1, wherein the Group V species is selected from the group consisting of nitrogen, phosphorus, arsenic, and antimony. [Invention 8] A.S.H. 3 The method according to claim 1, further comprising the use of [Invention 9] External AlCl 3 Lattice-matched Al, including the use of generators x In 1-x P and Al x Ga y In 1-x-y A method for the HVPE deposition of P, where x varies from 0 to 1. [Invention 10] External AlCl 3 10. The method of claim 9, wherein the source temperature of the generator is about 400 degrees Celsius. [Invention 11] AlCl 3 10. The method according to claim 9, wherein the molecule does not decompose during the deposition process. [Invention 12] 10. The method according to claim 9, wherein the deposition temperature is in the range of 620 to 700 degrees Celsius. [Invention 13] 10. The method according to claim 9, wherein the V / III ratio of the Al-containing III-V material is 10-300. [Invention 14] 10. The method of claim 9, wherein the Group V species is selected from the group consisting of nitrogen, phosphorus, arsenic, and antimony. [Invention 15] A.S.H. 3 The method of claim 9, further comprising the use of [Invention 16] External AlCl 3 An optoelectronic device manufactured using a method for depositing Al-containing III-V materials by HVPE using a generator. [Invention 17] External AlCl 3 17. An optoelectronic device according to claim 16, wherein the generator source temperature is about 400 degrees Celsius. [Invention 18] AlCl 3 17. An optoelectronic device according to claim 16, wherein the molecules do not decompose during the deposition process. [Invention 19] 17. The optoelectronic device according to claim 16, wherein the deposition temperature is in the range of 620 to 700 degrees Celsius. [Invention 20] The Al-containing III-V material is a lattice-matched Al x In 1-x P and Al x Ga y In 1-x-y 17. An optoelectronic device according to claim 16, comprising P.

Claims

1. external AlCl ３ A method for depositing Al-containing III-V materials by hydride vapor phase epitaxy (HVPE) using a generator, wherein AlCl 3 molecules do not decompose during the deposition process.

2. The external AlCl ３ 10. The method of claim 1, wherein the generator source temperature is 400 degrees Celsius.

3. The method of claim 1, wherein the deposition temperature is in the range of 620 to 700 degrees Celsius.

4. The Al-containing III-V material is Al ｘ G １－ｘ 2. The method of claim 1 , comprising:

5. The method of claim 4, wherein the Al-containing III-V material has a V / III ratio of 10-300.

6. The method of claim 1 , wherein the Group V species is selected from the group consisting of nitrogen, phosphorus, arsenic, and antimony.

7. A.S.H. ３ The method of claim 1 further comprising the use of

8. external AlCl ３ Lattice-matched Al, including the use of a generator ｘ In １－ｘ P and Al ｘ G ｙ In １－ｘ－ｙ A method for HVPE deposition of P, where x varies from 0 to 1, wherein AlCl 3 molecules do not decompose during the deposition process.

9. The external AlCl ３ 9. The method of claim 8, wherein the source temperature of the generator is 400 degrees Celsius.

10. The method of claim 8, wherein the deposition temperature is in the range of 620 to 700 degrees Celsius.

11. The method of claim 8, wherein the Al-containing III-V material has a V / III ratio of 10-300.

12. The method of claim 8 , wherein the Group V species is selected from the group consisting of nitrogen, phosphorus, arsenic, and antimony.

13. A.S.H. ３ The method of claim 8, further comprising the use of

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