Structure for in situ reflectance measurements during homoepitaxy

Abstract

The invention provides a semiconductor layered structure and a manufacturing method thereof. The semiconductor layered structure includes a substrate layer comprising a semiconductor material, a refractive index layer on the substrate layer, and at least one reflective layer on the refractive index layer, wherein the substrate layer and the reflective layer include substantially the same refractive index. The method includes growing a reflective layer on a refractive index layer via an epitaxial process; measuring a thickness of the reflective layer via a reflectometer; and terminating the epitaxial process at a desired thickness of the reflective layer.

Description

[0001] CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 63 / 357,931, filed on July 1, 2022, which is incorporated herein by reference in its entirety. Background Art

[0003] Nanoporous (NP) distributed Bragg reflectors (DBRs) can be formed after epitaxial growth by conductivity-selective electrochemical etching. By changing only the conductivity of the same semiconductor material, heavily doped (more conductive) layers can be selectively made porous while leaving lightly doped or undoped layers intact. The great advantage of this approach is that the complexity of conventional heteroepitaxy, i.e. growing semiconductor layers of different composition, can be replaced by homoepitaxy (growing the same material) of layers, differing only in the doping level of each layer. The layers used for NP DBRs are typically grown on substrates of the same material to minimize the creation of any microstructural defects and ensure the highest structural quality. When all of these factors come together, a unique challenge arises in the growth, namely, precise, repeatable and real-time control of the thickness of the layers in the construction of vertical-cavity surface-emitting lasers (VCSELs).

[0004] Thickness control is an important task in VCSEL manufacturing. Proper operation of VCSELs requires the preparation of highly reflective DBR mirrors with precisely controlled quarter-wavelength (1 / 4λ) layers of high and low refractive index, plus the need to control the position of the active gain region at the anti-node position within the vertical cavity. AlGaAs-based VCSELs, which have achieved great success in the infrared, include the use of in-situ reflectometers to monitor the evolution of reflectivity and the use of DBRs with sufficiently different optical refractive indices. However, there is a unique problem with the use of nanoporous DBRs, namely, the index contrast is formed after growth by conductivity-selective electrochemistry. During the growth of doped semiconductor layers with different conductivity on substrates made of the same semiconductor, the refractive index difference between the layers and the substrate is very small (Δn ~ 0.01). Therefore, reflectometers used for the growth of VCSELs (with DBRs formed after growth) no longer produce any reflection oscillations required to calibrate the growth rate and layer thickness.

[0005] Therefore, there is a need in the art to provide an article and method for performing in-situ reflectivity measurement in a substantially homoepitaxial process. The present invention addresses this need. Summary of the invention

[0006] In one aspect, the present invention includes a semiconductor layered structure, the semiconductor layered structure including: a substrate layer including a semiconductor material; a refractive index layer on the substrate layer; and at least one reflective layer on the refractive index layer; wherein the substrate layer and the reflective layer include substantially the same refractive index. In some embodiments, the semiconductor material includes gallium nitride (GaN), gallium arsenide (GaAs), or indium phosphide (InP).

[0007] In some embodiments, the refractive index layer comprises a semiconductor material doped with at least one other element. In some embodiments, the at least one other element comprises aluminum (Al), indium (In), or a combination thereof. In some embodiments, the concentration of the at least one other element in the refractive index layer is at least about 1×10 19 cm -3 .

[0008] In some embodiments, the refractive index layer comprises a semiconductor material alloyed with at least one other element. In some embodiments, the refractive index layer comprises AlGaN, InGaN, AlInN, or AlGaInN. In some embodiments, the refractive index layer is doped.

[0009] In some embodiments, the thickness of the refractive index layer is between (1 / 6n)λ and (1 / 2n)λ of the reflectometer source, where n is the refractive index of the refractive index layer.

[0010] In some embodiments, the substrate layer and the reflective layer are homoepitaxial.

[0011] In some embodiments, the reflective layer is nanoporous.

[0012] In some embodiments, the reflective layer includes a vertical cavity surface emitting laser (VCSEL).

[0013] In some embodiments, the difference between the refractive index of the refractive index layer and at least one of the substrate layer and the reflective layer is at least 0.01. In some embodiments, the difference between the refractive indices is between 0.01 and 0.8.

[0014] In another aspect, the invention comprises a method of producing a semiconductor layered structure according to any of the preceding claims, the method comprising growing a reflective layer on a refractive index layer via an epitaxial process; measuring the thickness of the reflective layer via a reflectometer; and terminating the epitaxial process at a desired thickness of the reflective layer. In some embodiments, the reflective layer and the refractive index layer comprise a refractive index difference of at least 0.01.

[0015] In some embodiments, the method further includes growing a refractive index layer on the substrate layer via an epitaxial process prior to growing the reflective layer; measuring the thickness of the refractive index layer via a reflectometer during the epitaxial process; and terminating the epitaxial process at a desired thickness of the refractive index layer. In some embodiments, the refractive index layer and the substrate layer include a refractive index difference of at least 0.01.

[0016] In some embodiments, the epitaxial process includes metal organic vapor phase epoxy.

[0017] In some embodiments, the semiconductor layered structure includes a nanoporous distributed Bragg reflector (DBR). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a fuller understanding of the nature and intended objectives of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals designate corresponding parts throughout the several views.

[0019] Figure 1 Schematic structures of light reflection at different interfaces according to embodiments of the present disclosure are depicted.

[0020] Figure 2 Depicted are simulated in-situ reflectivity evolution of hetero- and homoepitaxial gallium nitride (GaN) growth according to embodiments of the present disclosure.

[0021] Figure 3 Depicts various n according to embodiments of the present disclosure + Simulated in-situ reflectivity evolution of homoepitaxial GaN GaN layer. λ is 550nm. + The thickness of GaN varies between λ / 2n and λ / 6n.

[0022] Figure 4A -B depicts simulated in-situ reflectivity evolution of multiple low refractive index layers and high refractive index layers according to embodiments of the present disclosure. The curves represent high refractive index layers and low refractive index layers, respectively. λ is 550nm. (A) Multiple refractive index layers with μ / 4n thick low refractive index layers and high refractive index layers. (B) Multiple refractive index layers with thin low refractive index layers (thickness <λ / 4n) and thick high refractive index layers (thickness>λ / 4n).

[0023] Figure 5A -B depicts an embodiment according to the present disclosure in n - GaN template on n + and n - Reflectivity evolution measured during GaN growth. + The refractive index of GaN is lower than that of n- The refractive index of GaN, and therefore the reflectivity, increases with n + The growth time of GaN decreased with the growth of GaN. (A) The growth time was from 2600 seconds to 3000 seconds. (B) The growth time was from 2000 seconds to 4500 seconds.

[0024] Fig. 6A -B depicts an embodiment according to the present disclosure in n - u-AlGaN and n-GaN on GaN template - Reflectivity curve measured during GaN growth. Since the refractive index of u-AlGaN is lower than that of n - The refractive index of GaN, and therefore the reflectivity, decreases when u-AlGaN growth begins. (A) Growth time from 2400 to 3200 seconds. (B) Growth time from 2000 to 4500 seconds.

[0025] Fig. 7A -B depicts a plurality of n for wavelengths of (A) 550 nm and (B) 900 nm according to an embodiment of the present disclosure. + and n - Reflectivity curve measured during the GaN refractive index layer.

[0026] Fig. 8A -B depicts schematic epitaxial structures of NP GaN based VCSELs according to embodiments of the present disclosure. (A) As-grown VCSEL epitaxial structure. (B) Porosified VCSEL epitaxial structure.

[0027] Fig.9A -C depicts schematic diagrams of the porosification of the GaN layer. (A) Schematic epitaxial structure of a NP Ga NVCSEL according to an embodiment of the present disclosure. (B) Schematic diagram of the epitaxial structure of a NP Ga NVCSEL according to an embodiment of the present disclosure. - GaN distributed Bragg reflector (DBR) formed by the hole n + GaN layer. (C) Porous refractive index layer that aids reflection.

[0028] Fig. 10A -C depicts the structure and simulated reflectivity of NP GaN DBR. (A) Schematic structure of NPGaN DBR with a porous refractive index layer. (B) Simulated reflectivity at wavelengths between 350 and 1100 nm. (C) Simulated reflectivity at wavelengths between 400 and 460 nm.

[0029] Fig.11A -B depicts the reflection spectra of GaN DBR. (A) Simulated and experimentally measured reflection spectra of NP GaN DBR with porosity in the refractive index layer. (B) Reflection spectrum of a typical NP GaN DBR without porosity in the refractive index layer.

[0030] definition

[0031] The present invention may be best understood with reference to the following definitions.

[0032] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0033] Unless otherwise specified or apparent from the context, as used herein, the term "about" is understood to be within the normal tolerance range in the art, such as within 2 standard deviations of the mean. "About" may be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the specified value. Unless the context clearly dictates otherwise, all numerical values ​​provided herein are modified by the term about.

[0034] As used in the specification and claims, the terms "comprise," "comprising," "containing," "having," and the like may have the meanings ascribed to them in U.S. patent law, and may mean "include," "including," and the like.

[0035] Unless otherwise stated or obvious from the context, the term "or" as used herein should be understood to be inclusive.

[0036] The ranges provided herein are understood to be shorthand for all values ​​within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or subrange (and fractions thereof, unless the context clearly dictates otherwise) in 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50. DETAILED DESCRIPTION

[0037] Provided herein are structures and methods for performing in-situ reflectivity measurements during homoepitaxial growth. In some embodiments, the structure includes a substrate, a reflective layer, and a refractive index layer between the substrate and the reflective layer. In some embodiments, the reflective layer includes a distributed Bragg reflector (DBR). In some embodiments, the substrate and the reflective layer have the same or substantially the same refractive index (n). For example, in some embodiments, the substrate and the reflective layer are the same (homoepitaxial) or substantially the same material. Suitable materials for substrates and / or reflective layers include, but are not limited to, semiconductors (e.g., gallium nitride (GaN), gallium arsenide (GaAs), or indium phosphide (InP)), or any other suitable material for forming a DBR and / or a vertical cavity surface emitting laser (VCSEL).

[0038] Figure 1 (First figure) illustrates the basic principle of reflection oscillations, which are caused by constructive and destructive film interference between reflections at the air / film and film / substrate interfaces as the film thickness increases during growth. The larger the difference in refractive index (Δn), the larger the induced reflection oscillations for subsequent growth. For example, during heteroepitaxy, such as in the case of GaN on sapphire ( Figure 1 , second figure), the reflection oscillations from the interface between the substrate and the reflective layer can be seen. In contrast, during homoepitaxy, such as when the Al2O3 substrate is replaced by GaN ( Figure 1 , third figure), there is no longer any appreciable reflection from the buried interface and therefore no observable oscillations. Figure 2 This is further elucidated in simulations of heteroepitaxy and homoepitaxy, where when the refractive indices are the same or substantially the same (eg, in homoepitaxy), there are no reflection oscillations (flat curves) that serve as the basis for in situ monitoring of the growth rate.

[0039] However, according to embodiments disclosed herein, incorporating a refractive index layer between a substrate and a reflective layer (which includes the same or substantially the same refractive index) provides a refractive index change between them to induce oscillations during layer growth. In some embodiments, the refractive index difference between the refractive index layer and the substrate and / or the reflective layer includes, but is not limited to, at least 0.01, at least 0.02, at least 0.03, at least 0.04, at least 0.05, between 0.01 and 0.8, or any combination, subcombination, range, or subrange thereof. In some embodiments, the amplitude of oscillations induced by the refractive index layer is related to the material of the refractive index layer. Therefore, in some embodiments, the refractive index layer includes any suitable material for introducing a refractive index change compared to the substrate and / or the reflective layer. In some embodiments, the refractive index layer includes a doped or undoped material different from the substrate and / or the reflective layer. In some embodiments, the material includes a semiconductor (e.g., AlGaN, InGaN, AlInN, AlGaInN) alloyed with at least one other element. Additionally or alternatively, in some embodiments, the refractive index layer includes a doped layer of the same material as the substrate and / or the reflective layer (e.g., (Al, In) GaN, (Al, In) GaAs, or (Al, In) InP). For example, a (Al, In) GaN refractive index layer ( Figure 1 , Figure 4) provides a reflected signal that can oscillate with sufficient amplitude during subsequent epitaxy ( Figure 2 ), so that the growth rate can be accurately measured in situ even under essentially homoepitaxial conditions. In addition, in some embodiments, the refractive index layer can be electrochemically etched to form additional nanoporous mirrors, enhancing reflectivity.

[0040] Those skilled in the art will appreciate that different materials and different doping concentrations provide different levels of Δn. For example, in some embodiments, increasing n + - Refractive index layer (e.g. n + -GaN) will increase Δn, resulting in enhanced oscillation. In some embodiments, the concentration of the dopant in the refractive index layer is at least about 1×10 19 cm -3 , at about 1×10 19 cm -3 and 3×10 20 cm -3 or any suitable combination, subcombination, range or subrange thereof. + - and n - - The doping concentrations of the refractive index layers may include >3E19 and <1.5E19 cm -3 . Optionally, in some embodiments, n +-X refractive index layer is replaced by a doped or undoped AlX refractive index layer with a low Al composition (e.g., between 3% and 20%), where X is any suitable substrate, reflective layer or refractive index layer material. In these embodiments, increasing the Al composition and / or doping concentration increases Δn. In some embodiments, a reflective layer comprising a doped layer of the same material as the substrate and / or reflective layer provides a lower Δn and / or reduces complexity in epitaxy (e.g., build up of strain, degradation of morphology, or changes in growth parameters (pressure, temperature, growth rate)) compared to a reflective layer of a different material.

[0041] In some embodiments, the thickness of the refractive index layer can also be selected / adjusted to provide a desired / different oscillation amplitude. In some embodiments, when Δn is limited, the thickness can be selected / adjusted to provide an induced oscillation. In some embodiments, the thickness of the refractive index layer is between λ / 8n and λ / 2n, between λ / 8n and λ / 3n, between λ / 7n and λ / 2n, between λ / 7n and λ / 3n, between λ / 6n and λ / 2n, between λ / 6n (39nm) and λ / 3n (79nm), λ / 4n (59nm), or any combination, subcombination, range or subrange thereof. In some embodiments, the thickness of the refractive index layer is between λ / 6n (39nm) and λ / 3n (79nm). In some embodiments, the thickness of the refractive index layer is λ / 4n (59nm). In some embodiments, for a given Δn, (m / 2-1 / 4)λ / n thickness (where m is an integer) provides the maximum oscillation amplitude, while mλ / 2n thickness produces the minimum oscillation amplitude. In some embodiments, a thickness of (m / 2±1 / 12)λ / n reduces the oscillation amplitude by 50%.

[0042] In some embodiments, the thickness can be selected to provide a suitable reflected oscillation amplitude with limited refractive index contrast. For example, even when a heavily doped GaN refractive index layer (n~2.38 at 633nm) provides a limited contrast (Δn~0.1) with undoped GaN (n~2.44 at 633nm), the thickness of the refractive index layer can be selected to provide a sufficient induced oscillation amplitude. Figure 3 , which shows a simulation of the reflection oscillations indicated using refractive index layers of different thicknesses, a refractive index layer with a thickness of λ / 4n will give the largest oscillation amplitude. A thickness of λ / 6n or λ / 3n also produces good amplitudes, while a thickness of λ / 2n results in the smallest oscillations. Figure 4A The corresponding change in the oscillation amplitude as a function of the refractive index layer thickness is shown in , assuming that the reflectivity is measured at λ = 550 nm.

[0043] Additionally or alternatively, in some embodiments, multiple layers of reflective material may be used to increase the oscillation amplitude. Suitable layers include, but are not limited to, n+ -GaN / u-GaN, n + -GaN / n-GaN, n + -AlGaN / u-GaN, n + -AlGaN / n-GaN or u-AlGaN / u-GaN. For example, such as Figure 4A As illustrated, multiple refractive index layers with low refractive index layers and high refractive index layers of λ / 4n thickness can increase the oscillation amplitude. The low refractive index layer can be n + -GaN, n + -AlGaN or u-AlGaN. To minimize strain accumulation and / or surface degradation, multiple refractive index layers can be composed of thin low refractive index layers (thickness <λ / 4n) and thick high refractive index layers (thickness >λ / 4n) while maintaining a relative thickness of ~λ / 2n (Figure 4B). Even though the thin low refractive index layer reduces the oscillation amplitude, it can also reduce the complexity of epitaxy.

[0044] The structure according to the embodiments disclosed herein provides induced and sustained oscillations during GaN homoepitaxy with different refractive index layers and reflection wavelengths (λ=550nm and 900nm). For example, Figure 5A -B and 6A-B depict n + The reflectivity of GaN and u-AlGaN refractive index layers. - Compared with GaN, due to n + The refractive index of GaN and AlGaN is low, almost at n + When GaN (or AlGaN) starts to grow, the reflectivity decreases. Figure 5A -B and 6A-B show sustained oscillations of two wavelengths. Fig. 7A -B, may include multiple refractive index layers, which depict multiple n + In-situ reflection spectrum of GaN refractive index layer. Since the thickness is close to λ / 2n, the reflection amplitude increases with n + / n - The increase in GaN pairs increases.

[0045] Also provided herein is a VCSEL formed using a structure according to one or more embodiments disclosed herein. In some embodiments, the reflective layer includes a VCSEL. Fig. 8A -B depicts a schematic epitaxial structure of a NP GaN VCSEL. As illustrated therein, after porosification, n - GaN transforms into NPGaN, resulting in DBR formation ( Figure 8B ). In order to monitor and control the cavity and n - / n +The thickness of the GaN layer, the refractive index layer can be placed on n - / n + Below the GGaN layer ( Fig.9A -B). If the refractive index contains n + GaN or n + AlGaN, they can be porosified and act as additional n-side mirrors ( Fig. 9C ). According to the simulation, the porosity refractive index layer ( Fig. 10A ) can produce a broad peak at about 800nm ​​( Fig. 10B ), and their second harmonic oscillation peak can enhance the reflectivity at about 430nm ( Fig. 10C ). Fig.11A -B depicts the measured reflectivity of the NP DBR with and without porosification of the refractive index layer.

[0046] Further provided herein is a method for producing a nanoporous (NP) distributed Bragg reflector (DBR). In some embodiments, the method includes growing a reflective layer on a refractive index layer via an epitaxial process; measuring the thickness of the reflective layer via a reflectometer; and maintaining the thickness of the reflective layer by terminating another epitaxial process. In some embodiments, before growing the reflective layer, the method includes growing a refractive index layer on a substrate layer via an epitaxial process; during the epitaxial process, measuring the thickness of the refractive index layer via a reflectometer; and maintaining the thickness of the refractive index layer by terminating the epitaxial process. In some embodiments, the epitaxial process includes a metal organic vapor phase epoxy.

[0047] Embodiments disclosed herein enable in-situ thickness monitoring and control in basic homoepitaxial structures, including but not limited to semiconductor layer thickness during the manufacture of VCSELs made of distributed Bragg reflectors (e.g., GaN DBRs on GaN substrates, InP DBRs on InP substrates) made of the same material as the substrate. The ability to measure and control homoepitaxial layer thickness in-situ further enables reliable and repeatable production of VCSELs. In addition, the use of an additional refractive index bottom layer greatly improves the manufacturability of VCSELs made of porous layers.

[0048] Equivalent changes

[0049] While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

[0050] Examples of implementation methods

[0051] In some embodiments, this description relates to the following non-limiting embodiments:

[0052] Embodiment 1: A semiconductor layered structure comprising: a substrate layer comprising a semiconductor material; a refractive index layer on the substrate layer, the refractive index layer comprising a doped form of the semiconductor material; and at least one reflective layer on the refractive index layer; wherein the substrate layer and the reflective layer comprise substantially the same refractive index.

[0053] Embodiment 2: The semiconductor layered structure according to Embodiment 1, wherein the semiconductor material includes gallium nitride (GaN), gallium arsenide (GaAs), or indium phosphide (InP).

[0054] Embodiment 3: The semiconductor layered structure of any preceding embodiment, wherein the thickness of the refractive index layer depends on the wavelength of the reflectometer source.

[0055] Embodiment 4: The semiconductor layered structure of any of the preceding embodiments, wherein the thickness of the refractive index layer is between (1 / 6n)λ and (1 / 2n)λ of a reflectometer source, where n is the refractive index of the refractive index layer.

[0056] Embodiment 5: The semiconductor layered structure according to any of the preceding embodiments, wherein the refractive index layer is doped with at least one other element including Al, In, or a combination thereof.

[0057] Embodiment 6: The semiconductor layered structure according to any of the preceding embodiments, wherein the concentration of the n-dopant in the refractive index layer is about 1×10 19 cm -3 or higher, or about 1×10 19 -cm -3 Up to 3×10 20 cm -3 within the range.

[0058] Embodiment 7: The semiconductor layered structure according to any of the preceding embodiments, wherein the substrate layer and the reflective layer are homoepitaxial.

[0059] Embodiment 8: The semiconductor layered structure according to any of the preceding embodiments, wherein the reflective layer is nanoporous.

[0060] Embodiment 9: The semiconductor layered structure of any of the preceding embodiments, wherein the nanoporous layer comprises a vertical cavity surface emitting laser (VCSEL).

[0061] Embodiment 10: The semiconductor layered structure of any of the preceding embodiments, wherein the difference between the refractive index of the refractive index layer and at least one of the substrate layer and the reflective layer is at least 0.01.

[0062] Embodiment 11: The semiconductor layered structure of any of the preceding embodiments, wherein the difference between the refractive index of the refractive index layer and at least one of the substrate layer and the reflective layer is between 0.01 and 0.8.

[0063] Embodiment 12: A semiconductor layered structure comprising: a substrate layer comprising a semiconductor material; a refractive index layer on the substrate layer, the refractive index layer comprising a semiconductor material alloyed with at least one other element; and at least one reflective layer on the refractive index layer; wherein the substrate layer and the reflective layer comprise substantially the same refractive index.

[0064] Embodiment 13: The semiconductor layered structure according to Embodiment 12, wherein the semiconductor material includes gallium nitride (GaN), gallium arsenide (GaAs), or indium phosphide (InP).

[0065] Embodiment 14: The semiconductor layered structure of Embodiment 12 or 13, wherein the semiconductor material comprises GaN and the refractive index layer comprises another element, such as indium or aluminum.

[0066] Embodiment 15: The semiconductor layered structure of any of Embodiments 12-14, wherein the thickness of the refractive index layer depends on the wavelength of the reflectometer source.

[0067] Embodiment 16: The semiconductor layered structure of any one of Embodiments 12-15, wherein the thickness of the refractive index layer is between (1 / 6n)λ and (1 / 2n)λ of a reflectometer source, where n is the refractive index of the refractive index layer.

[0068] Embodiment 17: The semiconductor layered structure according to any one of Embodiments 12 to 16, wherein the substrate layer and the reflective layer are homoepitaxial.

[0069] Embodiment 18: The semiconductor layered structure of any one of Embodiments 12-17, wherein the reflective layer is nanoporous.

[0070] Embodiment 19: The semiconductor layered structure of any one of Embodiments 12-18, wherein the nanoporous layer comprises a vertical cavity surface emitting laser (VCSEL).

[0071] Embodiment 20: The semiconductor layered structure of any one of Embodiments 12-19, wherein the difference between the refractive index of the refractive index layer and at least one of the substrate layer and the reflective layer is at least 0.01.

[0072] Embodiment 21: The semiconductor layered structure of any one of Embodiments 12-20, wherein the difference between the refractive index of the refractive index layer and at least one of the substrate layer and the reflective layer is between 0.01 and 0.8.

[0073] Embodiment 22: A method for producing a semiconductor layered structure as described in any of the preceding embodiments, the method comprising growing a reflective layer on a refractive index layer via an epitaxial process; measuring the thickness of the reflective layer via a reflectometer; and terminating the epitaxial process at the desired thickness of the reflective layer.

[0074] Embodiment 23: The method of embodiment 22, wherein the reflective layer and the refractive index layer comprise a refractive index difference of at least 0.01.

[0075] Embodiment 24: The method according to embodiment 22 or 23 further includes growing a refractive index layer on the substrate layer via an epitaxial process before growing the reflective layer; measuring the thickness of the refractive index layer via a reflectometer during the epitaxial process; and terminating the epitaxial process at the desired thickness of the refractive index layer.

[0076] Embodiment 25: The method of any one of Embodiments 22-24, wherein the refractive index layer and the substrate layer comprise a refractive index difference of at least 0.01.

[0077] Embodiment 26: The method of any one of Embodiments 22-25, wherein the epitaxial process comprises metal organic vapor phase epoxy.

[0078] Embodiment 27: The method of any one of Embodiments 22-26, wherein the semiconductor layered structure comprises a nanoporous distributed Bragg reflector (DBR).

[0079] Incorporated by Reference

[0080] All patents, published patent applications, and other references cited herein are expressly incorporated by reference in their entirety.

Claims

1. A semiconductor layered structure comprising: a substrate layer comprising a semiconductor material; a refractive index layer on the substrate layer; as well as at least one reflective layer on the refractive index layer; Wherein the substrate layer and the reflective layer comprise substantially the same refractive index. 2 . The semiconductor layered structure according to claim 1 , wherein the semiconductor material comprises gallium nitride (GaN), gallium arsenide (GaAs), or indium phosphide (InP).

3. The semiconductor layered structure of claim 1, wherein the refractive index layer comprises the semiconductor material doped with at least one other element. The semiconductor layered structure of claim 3 , wherein the at least one other element comprises Al, In, or a combination thereof.

5. The semiconductor layered structure of claim 1, wherein the concentration of the at least one other element in the refractive index layer is at least about 1×10 19 cm -3 .

6. The semiconductor layered structure of claim 1, wherein the refractive index layer comprises a semiconductor material alloyed with at least one other element. 7 . The semiconductor layered structure according to claim 6 , wherein the refractive index layer comprises AlGaN, InGaN, AlInN or AlGaInN. The semiconductor layered structure of claim 6 , wherein the refractive index layer is doped.

9. The semiconductor layered structure of claim 1, wherein the refractive index layer has a thickness between (1 / 6n)λ and (1 / 2n)λ of a reflectometer source, where n is the refractive index of the refractive index layer.

10. The semiconductor layered structure of claim 1, wherein the substrate layer and the reflective layer are homoepitaxial.

11. The semiconductor layered structure of claim 1, wherein the reflective layer is nanoporous.

12. The semiconductor layered structure of any one of the preceding claims, wherein the reflective layer comprises a vertical cavity surface emitting laser (VCSEL).

13. The semiconductor layered structure of claim 1, wherein a difference between a refractive index of the refractive index layer and at least one of the substrate layer and the reflective layer is at least 0.

01.

14. The semiconductor layered structure of claim 13, wherein the difference between the refractive indices is between 0.01 and 0.

8.

15. A method of producing a semiconductor layered structure according to any one of the preceding claims, the method comprising: Growing a reflective layer on the refractive index layer through an epitaxial process; measuring the thickness of the reflective layer via a reflectometer; as well as The epitaxial process is terminated at a desired thickness of the reflective layer.

16. The method of claim 15, wherein the reflective layer and the refractive index layer comprise a refractive index difference of at least 0.

01.

17. The method according to claim 15, further comprising, before growing the reflective layer: Growing the refractive index layer on the substrate layer via an epitaxial process; During the epitaxial process, measuring the thickness of the refractive index layer via a reflectometer; and The epitaxial process is terminated at a desired thickness of the refractive index layer.

18. The method of claim 17, wherein the refractive index layer and the substrate layer comprise a refractive index difference of at least 0.

01.

19. The method of any one of claims 15 to 18, wherein the epitaxial process comprises metal organic vapor phase epoxy.

20. The method of any one of claims 15 to 19, wherein the semiconductor layered structure comprises a nanoporous distributed Bragg reflector (DBR).

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