Abstract:
A method of selective dry etching of N-face (Al,In,Ga)N heterostructures through the incorporation of an etch-stop layer into the structure, and a controlled, highly selective, etch process. Specifically, the method includes: (1) the incorporation of an easily formed, compatible etch-stop layer in the growth of the device structure, (2) the use of a laser-lift off or similar process to decouple the active layer from the original growth substrate, and (3) the achievement of etch selectivity higher than 14:1 on N-face (Al,In,Ga)N.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/551,181, filed on Oct. 25, 2011, by James S. Speck, Evelyn L. Hu, Claude C. A. Weisbuch, Yong Seok Choi, Gregor Koblmuller, Michael Iza, and Christophe Hurni, and entitled “SELECTIVE DRY ETCHING OF N-FACE (Al,In,Ga)N HETEROSTRUCTURES,” attorneys&#39; docket number 30794.413-US-P1 (2007-460-1), which application is hereby incorporated by reference herein. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
       [0002]    This invention was made with Government support under Grant No. DE-FC26-06NT42857 awarded by the U.S. Department of Energy. The Government has certain rights in this invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The invention is related generally to the field of electronic and optoelectronic devices, and more particularly, to selective dry etching of nitrogen face (N-face) (Al,In,Ga)N heterostructures. 
         [0005]    2. Description of the Related Art 
         [0006]    (Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [Ref. X]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.) 
         [0007]    Typical GaN-based light-emitting diodes (LEDs) are planar structures, where a several-micron-thick GaN template and InGaN/GaN quantum-well active region are grown on a lower index Sapphire substrate. The top air/GaN interface and the GaN/Sapphire interface serve as mirrors to form discrete bound states for photons, so called guided modes. As these guided modes propagate parallel to the planar geometry, the direct emission in the vertical direction is low, i.e., a few percent of the total emission. Therefore, the integration (packaging) of external optics is necessary to retain the vertical emission. 
         [0008]    Submicron-thick micro-cavity light emitting diodes (MCLEDs) [Ref 1] and photonic-crystal-MCLEDs (PC-MCLEDs) [Ref 2] promise superior performance to conventional LEDs. Tailoring of the modal characteristics can lead to enhancement of spontaneous emission [Ref 3], spectral purity [Ref 4], and directionality [Refs. 5-6], which contribute to increased brightness and energy efficiency. This invention addresses critical challenges in the fabrication of such devices, enabling commercial realization of these LEDs with exceptional extraction efficiency. 
         [0009]    In more conventional III-V materials, such as GaAs and InP, highly efficient microcavity optical devices with controlled light emission can be formed through the monolithic growth of high reflectivity mirrors, and a thin active region whose thickness and composition are controlled by the precision of the epitaxial growth technique. Such techniques are not practical, or easily implemented or accomplished, in GaN-based LEDs and lasers. 
         [0010]    For GaN-based LEDs and lasers, a high quality underlying mirror is required to direct light away from the substrates, which serves as a loss channel for the generated light. Although AlGaN/GaN Distributed Bragg Reflectors (DBRs) have been formed, the low index contrast between AlGaN/GaN requires high Al composition and a large number of DBR periods for a highly reflective mirror [Ref 7]. The inherent strain in this heterostructure leads to the formation of cracks and other defects in the mirror structure [Ref. 8]. 
         [0011]    The lossy effects of the substrate may be addressed through removal of the active layer from the substrate, through techniques like laser lift-off (LLO) [Refs. 9-10]. The lift-off structure can then be bonded to a different substrate, and appropriate dielectric DBRs deposited [Ref 11]. However, a certain minimum thickness (several microns) between the active area and the original substrate is required to ensure the integrity of the active region during the lift-off process. Precision control of the post LLO etch in the vertical direction determines the thickness of the MCLED; uniformity of the etch in the lateral direction will ensure a high yield of devices. Such etch control is a critical factor in the fabrication and ultimate manufacturability of such devices. 
         [0012]    Recently, T. Fujii et al. [Ref 1] have demonstrated submicron-thick MCLEDs by utilizing the LLO technique and the nonselective thinning process, i.e., reactive ion etching (RIE) and successive chemical mechanical polishing (CMP) [Ref. 12]. This processing scheme has further been a basis for exploring PC-MCLEDs [Ref 2]. However, the adopted thinning method lacks reproducibility, precision, and scalability in controlling the microcavity thickness. 
         [0013]    The present invention proposes the incorporation of an etch-stop layer into the device structure, and a controlled, highly selective, etch process. Specifically, the present invention includes: (1) the incorporation of an easily formed, compatible etch-stop layer in the growth of the device structure, (2) the use of a laser-lift off or similar process to decouple the active layer from the original ‘growth’ substrate, and (3) the achievement of etch selectivity higher than 14:1 on N-face (Al,In,Ga)N. 
         [0014]    For a GaN structure, In x Ga 1-x N or Al x Ga 1-y N layers can be epitaxially incorporated, generally with a thickness commensurate with a critical thickness [Ref. 13]. Generally, it is expected that the higher the chemical difference between etch stop layer and the surrounding material, the higher the achievable dry-etch or wet-etch selectivity. 
         [0015]    The choices of selective wet etches are limited, although some high-temperature etches have been found for AlGaN and photoelectrochemical etching has been shown to be effective for a broad composition of (Al,Ga,In)N. There are a number of dry or gas-phase etches; in general, all such processes, e.g., RIE, inductively coupled plasma (ICP) etching, etc., contain a chemical component and an ion-assisted (physical) component. 
         [0016]    Etch selectivities for the Group-III face (III-face) III-nitride materials have been demonstrated by, e.g., S. A. Smith et al. [Ref 14] using an ICP process with Cl 2  and Ar to etch GaN, AlGaN, and AlN. S. J. Pearton et al. [Ref 15] have utilized etch gases of Cl 2 , BCl 3 , SF 6 , and Ar for ICP etching of GaN, AlN, and InN. The maximum etch selectivity of 6:1 was obtained for GaN:AlN by the Cl 2 -based ICP. 
         [0017]    The demonstration of selective etches for the III-face does not guarantee etch behavior of the N-face; differences in etch behavior of the two faces have already been suggested in Refs. 16-18. In fact, I. Waki et al. [Ref 19] have investigated the ICP etching of (0001) (-c) N-face GaN, which was obtained by LLO process. The etch rate of ˜7 nm/min was obtained with the flow rates of 20 sccm for BCl 3  and 5 sccm for SF 6 , the chamber pressure of 4 Pa, and the source and bias powers of 250 W and 175 W, respectively. However, the etch selectivity was not achieved. 
         [0018]    Thus, there is a need in the art for improved methods for nano-precision etching of GaN, AlGaN, InGaN, and AlInGaN, in the fabrication of electronic and optoelectronic devices. The present invention satisfies this need. Specifically, the present invention provides for selective dry etching of N-face (Al,In,Ga)N heterostructures. 
       SUMMARY OF THE INVENTION 
       [0019]    To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method for selective dry etching of N-face (Al,In,Ga)N heterostructures through the incorporation of an etch-stop layer into the structure, and a controlled, highly selective, etch process. Specifically, the present invention includes: (1) the incorporation of an easily formed, compatible etch-stop layer in the growth of the device structure, (2) the use of a laser-lift off or similar process to decouple the active layer from the original growth substrate, and (3) the achievement of etch selectivity higher than 14:1 on N-face (Al,In,Ga)N. The present invention also encompasses devices fabricated according to this method. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
           [0021]      FIG. 1(   a ) are simplified schematic diagrams showing the steps of a method of the present invention, used for a conventional GaN-based LED grown on a Sapphire substrate, including laser debonding of the Sapphire substrate, followed by selective etching of a GaN template utilizing an etch stop layer. 
           [0022]      FIG. 1(   b ) is a Scanning Electron Micrograph (SEM) of a test material with the Al 0.30 Ga 0.70 N etch stop layer grown by Molecular Beam Epitaxy (MBE). 
           [0023]      FIGS. 2(   a )- 2 ( d ) are simplified schematic diagrams showing the steps of a method of the present invention, used to verify the selective removal of N-face GaN by BCl 3  and SF 6  based ICP etching. 
           [0024]      FIG. 3  is a SEM image of the etch surface after the 15 min ICP etching. 
           [0025]      FIGS. 4(   a ) and  4 ( b ) are SEM images taken after ( FIG. 4(   a )) the 20 min and ( FIG. 4(   b )) the additional 20 min (total 40 min) ICP etching; processes, wherein the initial 20 min ICP etching stopped at the Al 0.30 Ga 0.70 N etch stop layer, which could withstand the additional 20 min ICP process at the same condition. 
           [0026]      FIGS. 5(   a )- 5 ( d ) are SEM images showing the correlation between the micro-cone density and the Al composition (x) in the Al x Ga 1-x N layer, wherein  FIG. 5(   a ) shows x=0.15;  FIG. 5(   b ) shows x=0.15;  FIG. 5(   c ) shows x=0.30; and  FIG. 5(   d ) shows x=0.51; and wherein the samples were processed at the same ICP condition concurrently. 
           [0027]      FIGS. 6(   a )- 6 ( h ) are simplified schematic diagrams showing the steps of a process, according to one embodiment of the present invention, used to fabricate MCLEDs and/or PC-MCLEDs for an epi-structure grown on a Sapphire substrate. 
           [0028]      FIGS. 7(   a )- 7 ( i ) are simplified schematic diagrams showing the steps of a process, according to one embodiment of the present invention, used to fabricate MCLEDs and/or PC-MCLEDs for an epi-structure grown on a free-standing GaN substrate. 
           [0029]      FIG. 8  are simplified schematic diagrams showing the steps of a process, according to one embodiment of the present invention, used to fabricate a thin Group-III nitride-based film for efficient thermal management with a passive temperature control unit (heat dissipater) or an active temperature control unit (thermoelectric temperature controller). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    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. 
         [0031]    Overview 
         [0032]    This invention describes a method to utilize controllable and extremely high etch selectivities of (Al,In,Ga)N heterostructures for devices of those materials requiring fabrication with nano-scale precision. Specifically, this invention relates to a nano-precision etching method with reproducibility and scalability for GaN and its ternary and quaternary compounds incorporating aluminum and indium (AlGaN, InGaN, AlInGaN), which are essential for visible and ultraviolet optoelectronic devices and high-power electronic devices. 
         [0033]    In one embodiment, the present invention discloses a method for dry etch selectivity in fabricating an opto-electronic device, by etching one or more nitride layers having an (Al,In,Ga)N etch-stop layer containing at least some Aluminum (Al), wherein the nitride layers and etch-stop layer comprise layers of dissimilar (Al,Ga,In)N composition and the nitride layers are etched at a higher rate than the etch-stop layer. 
         [0034]    Other aspects of this embodiment include:
       The nitride layers and etch-stop layer comprise layers having varying or graded compositions.   The etching is performed on an etch surface that is a (0001) (-c) Nitrogen-face (N-face) of the nitride layers, wherein the nitride layers comprise c-plane GaN layers and the etch surface is an as-grown (0001) (-c) N-face of the c-plane GaN layers.   The etch-stop layer comprises an Al x Ga 1-x N layer with x&gt;0, and more preferably, 0.1&lt;x&lt;0.5.   The etch-stop layer has a thickness that is greater than 1 nm, and more preferably, a thickness that is between 10 nm and 100 nm.   The nitride layers are etched by ICP etching using etch gases of SF 6 , BCl 3 , Cl 2 , Ar, or O 2  at a source power P S  and bias power P B , where 0&lt;P S &lt;200 W, 0&lt;P B &lt;100 W and P B &lt;P S .   The ICP etching is carried out along with an initial chemical mechanical polishing or RIE using etch gases of SF 6 , BCl 3 , Cl 2 , Ar, or O 2 .       
 
         [0041]    In another embodiment, the present invention discloses a method for dry etch selectivity in fabricating an opto-electronic device, by etching one or more nitride layers having an (Al,In,Ga)N etch-stop layer containing at least some Indium (In), wherein the nitride layers and etch-stop layer comprise layers of dissimilar (Al,Ga,In)N composition and the nitride layers are etched at a higher rate than the etch-stop layer. 
         [0042]    Other aspects of this embodiment include:
       The etch-stop layer is used as an etch stop over a Gallium face (Ga-face) or a Nitrogen face (N-face) of the nitride layers.   An etch product InCl 3  provides a dry etch selectivity for a chlorine-based etch gas.   An etch product InF 3  provides a dry etch selectivity for a fluorine-based etch gas.       
 
       TECHNICAL DESCRIPTION 
       [0046]    A particular embodiment of the present invention involves the formation of an AlGaN etch-stop layer. The device fabrication process and the role of the etch-stop layer are shown in  FIG. 1(   a ), which shows a sequence of steps comprising: (1) growth of a conventional GaN-based LED on a c-plane Sapphire substrate  100  including a GaN template  102 , an etch stop layer  104  and an active region  106 ; (2) laser debonding of the Sapphire substrate  100  and bonding of a submount  108 ; and (3) selective etching of the GaN template  102  utilizing the etch stop layer  104 . The etch gas used must (1) etch GaN at a fairly substantial rate, (2) much higher than the rate of etching of the AlGaN. A choice of etch gas is a fluorine-containing gas, wherein Al is known to form the nonvolatile AlF 3  layer during fluorine-based dry etching, and another choice of etch gas is a chlorine-containing gas, wherein Al is known to form the nonvolatile AlCl 3  layer during chlorine-based dry etching. This knowledge is specifically developed further for the selective etching of (Al,In,Ga)N heterostructures, to achieve a minimal (˜0) etch rate of the AlGaN, with a measurable etch rate for GaN. 
         [0047]    An alternative embodiment of the present invention involves the formation of an InGaN etch-stop layer in a similar structure and using a similar process to perform selective etching of the GaN template utilizing the etch stop layer. In this embodiment, the etch gas used must (1) etch GaN at a fairly substantial rate, (2) much higher than the rate of etching of the InGaN. Similar to Al, the choice of etch gas is a fluorine-containing gas, wherein In is known to form the nonvolatile InF 3  layer during fluorine-based dry etching, and another choice of etch gas is a chlorine-containing gas, wherein In is known to form the nonvolatile InCl 3  layer during chlorine-based dry etching. 
         [0048]    The inventors have specifically investigated the etch selectivity between N-face GaN and an Al x Ga 1-x N etch stop layer. For a detailed characterization of etch selectivity, the inventors have grown samples with Al x Ga 1-x N etch stop layers of various Al compositions (e.g., x=15%, 30%, and 51%) by MBE on a freestanding GaN substrate. The target thicknesses of Al x Ga 1-x N layers were 60 nm, 30 nm, and 10 nm, respectively. Because of the lattice mismatch, there is an inverse relationship between the percentage of Al and achievable etch-stop thickness. In particular, N-face GaN is grown to mimic the thinning process of [Ref. 1]; the GaN template obtained by the LLO process is N-face.  FIG. 1(   b ) shows the cross section of one sample with an Al 0.30 Ga 0.70 N layer that is about 25 nm thick. 
         [0049]    The experimental procedure is illustrated in  FIGS. 2(   a )- 2 ( d ) and described as follows: 
         [0050]    (1) Growth on a GaN substrate  200 , including a GaN layer  202 , an Al x Ga 1-x N layer  204  and an N-face GaN layer  206 , followed by patterning photoresist mesas  208  on the N-face GaN  206  using optical lithography, as shown in  FIG. 2(   a ). 
         [0051]    (2) Introducing a 200 nm-thick SrF 2  mask layer  210  by e-beam deposition and a lift-off technique to remove the photoresist  208 , as shown in  FIG. 2(   b ). 
         [0052]    (3) Pre-cleaning of the exposed N-face GaN  206  with BCl 3  based dry etching using an ICP etching system (Panasonic ICP Model E640), as shown in  FIG. 2(   c ). 
         [0053]    (4) Selective removal of the exposed N-face GaN  206  using BCl 3  and SF 6  based ICP etching, as shown in  FIG. 2(   d ). 
         [0054]    (5) Inspection of the etch rate and etch damage on the surface by scanning electron microscopy (SEM) and atomic force microscopy (AFM). 
         [0055]      FIG. 3  is a SEM image of the etch surface after the 15 min ICP etching. As the etch gases, 20 sccm BCl 3  and 5 sccm SF 6  were used. The chamber pressure was 5 Pa. The source and bias powers were 250 W and 60 W, respectively. The low bias power is used to minimize the sputter-removal of the otherwise non-volatile AlF 3  formed at the surface, which retards further etching of the AlGaN layer. The etch surface is characterized by a flat region (the Al 0.30 Ga 0.70 N etch stop layer) and some submicron-sized cones and dots. 
         [0056]    To investigate the etch damage on the Al 0.30 Ga 0.70 N surface, the inventors carried out an extended 20 minutes of ICP etching for another sample at the same ICP condition. The surface quality of the Al 0.30 Ga 0.70 N etch stop layer seems to be similar to that from 15 minutes of ICP etching, as shown in  FIG. 4(   a ). An additional 20 minutes (for a total of 40 minutes) of ICP etching resulted in some sputter removal of the surface, as shown in  FIG. 4(   b ). In both cases, the etch depth is almost the same as that of the 15 minutes of ICP etching. This suggests an etch selectivity of at least 14 to 1 between N-face GaN and Al 0.30 Ga 0.70 N. 
         [0057]    The correlation between the etch selectivity and the sample structure, i.e., the Al composition (x) in the Al x Ga 1-x N layer, was also investigated by the inventors.  FIGS. 5(   a ) and  5 ( b ) are SEM images that show the etch results of a sample with a 60 nm thick Al 0.15 Ga 0.85 N layer.  FIGS. 5(   c ) and  5 ( d ) are SEM images that show the etch results of samples with 30 nm thick Al 0.30 Ga 0.70 N and 10 nm thick Al 0.51 Ga 0.49 N layers. The thickness of the N-face GaN was 260 nm for all samples with different Al x Ga 1-x N etch stop layers. The samples were processed at the same ICP conditions concurrently. 
         [0058]    All the Al x Ga 1-x N layers demonstrate very robust etch-stopping behavior, as shown in  FIGS. 5(   a )- 5 ( d ). Interestingly, it appears that there is a correlation between the number of submicron-sized cones and the Al composition (x). In the inventors&#39; test samples, the N-face GaN layer was grown on the Al x Ga 1-x N etch stop layer. A larger lattice mismatch from a higher Al composition would result in a GaN layer with poorer material quality such as pits or threading dislocation, and a subsequent formation of submicron-sized cones. 
       EMBODIMENTS OF THE INVENTION 
       [0059]    Embodiments of the present invention may involve the fabrication of MCLEDs or PC-MCLEDs. The fabrication procedures for the epi-structures grown on two types of substrates, i.e., Sapphire and GaN, are described below. 
         [0060]      FIGS. 6(   a )- 6 ( h ) are simplified schematic diagrams showing the steps of a process, according to one embodiment of the present invention, used to fabricate MCLEDs and/or PC-MCLEDs for an epi-structure grown on a Sapphire substrate  600 . The steps of this first fabrication procedure are described as follows: 
         [0061]    (1) Growth of the epi-structure with a GaN layer  602 , an Al x Ga 1-x N etch stop layer  604  and a GaN/InGaN/GaN active region  606  on the Sapphire substrate  600  by metalorganic chemical vapor deposition (MOCVD), as shown in  FIG. 6(   a ). 
         [0062]    (2) Metal wafer bonding to a submount  608  using bonding metals  610  such as Tin (Sn) and Gold (Au), as shown in  FIG. 6(   b ). 
         [0063]    (3) Laser debonding of the Sapphire substrate  600 , as shown in  FIG. 6(   c ). 
         [0064]    (4) Initial thinning process utilizing a chemical mechanical polishing or non-selective (Cl and Ar-based) dry-etch process with the ICP system (Panasonic ICP Model E640), as shown in  FIG. 6(   d ). 
         [0065]    (5) Pre-cleaning of the N-face GaN  602  surface with BCl 3  based dry etching with the ICP system (not shown). 
         [0066]    (6) Selective thinning of the N-face GaN  602  with BCl 3  and SF 6 -based ICP etching, as shown in  FIG. 6(   e ). 
         [0067]    (7) Post-cleaning of GaN microcones on the surface of Al x Ga 1-x N layer  604  with SF 6  based ICP etching, as shown in  FIG. 6(   f ). 
         [0068]    (8) Rinse with HCl, de-ionized water, acetone, and isopropanol, as shown in  FIG. 6(   g ). 
         [0069]    (9) Cathode  612  deposition to form an MCLED, as shown in  FIG. 6(   h ), or 
         [0070]    (10) Photonic-crystal (PC) formation in the etch stop layer  604  and cathode  612  deposition to form a PC-MCLED, also as shown in  FIG. 6(   h ). 
         [0071]      FIGS. 7(   a )- 7 ( h ) are simplified schematic diagrams showing the steps of a process, according to one embodiment of the present invention, used to fabricate MCLEDs and/or PC-MCLEDs for an epi-structure grown on a free-standing GaN substrate  700 . The steps of this second fabrication procedure are described as follows: 
         [0072]    (1) Growth of the epi-structure with a GaN layer  702 , an Al x Ga 1-x N etch stop layer  704  and a GaN/InGaN/GaN active region  706  on the GaN substrate  700  by MOCVD, as shown in  FIG. 7(   a ). 
         [0073]    (2) Wafer bonding to a temporary glass submount  708  using an epoxy glue  710 , which is soluble by acetone, as shown in  FIG. 7(   b ). 
         [0074]    (3) An initial thinning process utilizing a chemical mechanical polishing or non-selective (Cl and Ar-based) dry-etch process with the ICP system (Panasonic ICP Model E640), as shown in  FIG. 7(   c ). 
         [0075]    (4) Pre-cleaning of the N-face GaN  702  surface with BCl 3  based dry etching with the ICP system (not shown). 
         [0076]    (5) Selective thinning of the N-face GaN  702  with BCl 3  and SF 6 -based ICP etching, as shown in  FIG. 7(   d ). 
         [0077]    (6) Post-cleaning of GaN microcones on the surface of the Al x In 1-x N etch stop layer  704  with a SF 6  based ICP etching, as shown in  FIG. 7(   e ). 
         [0078]    (7) Rinse with HCl, de-ionized water (not shown). 
         [0079]    (8) Introducing a thick metal submount  712 , which serves as a cathode and a mirror, by electron-beam deposition or electroplating, as shown in  FIG. 7(   f ). 
         [0080]    (9) Debonding the sample from the submount  708  using a solvent, such as acetone, as shown in  FIG. 7(   g ). 
         [0081]    (10) Anode  714  deposition, such as a transparent Pd/Au metal or indium-tin-oxide (ITO) contact, to form an MCLED, as shown in  FIG. 7(   h ), or 
         [0082]    (11) Photonic crystal formation in the active region  706  and anode  714  deposition, such as a transparent Pd/Au metal or indium-tin-oxide (ITO) contact, to form a PC-MCLED, also as shown in  FIG. 7(   i ). 
         [0083]    Another embodiment is the fabrication of a thin nitride-based film for efficient thermal management combined with a submount made of good thermal conductors. This can be integrated with a passive temperature control unit (e.g., heat dissipater) as well as an active temperature control unit (e.g., thermoelectric temperature controller), as shown in  FIG. 8 . Specifically,  FIG. 8  are simplified schematic diagrams showing the steps of a process, according to one embodiment of the present invention, used to fabricate a thin Group-III nitride-based film for efficient thermal management with a passive temperature control unit (heat dissipater) or an active temperature control unit (thermoelectric temperature controller). The steps of this fabrication procedure include: (1) growth on a Sapphire substrate  800  of a ˜4 μm GaN template  802 , an AlGaN etch stop layer  804 , and a thin active layer  806 , (2) bonding of a submount  808  and laser debonding of the Sapphire substrate  800 , (3) removal of the GaN template  802  by selective etching, and finally, the fabrication of (4) a passive temperature control comprising a heat dissipater  810  (shown in both side and top views) or (5) an active temperature control comprising a thermoelectric temperature controller  812  (shown in both side and top views). These structures may comprise a device (e.g., MCLEDs or PC-MCLEDs), as well as a template for overgrowth or vertical integration of other device structures. 
         [0084]    Other embodiments would include nitride semiconductor lasers as well as electronic devices that require the etch selectivity between N-face nitride layers and an Al x In 1-x N etch stop layer. 
         [0085]    Some examples of the many products that would benefit from the present invention include III-nitride-based MCLEDs, PC-MCLEDs, and High-Electron Mobility Transistors (HEMTs). 
         [0086]    Other are areas that would benefit from the present invention include: 
         [0087]    (1) Optimization of MOCVD growth for (Al,In,Ga)N heterostructures with a thin (400 nm) Al x Ga 1-x N etch stop layer where 0.1&lt;x&lt;0.5. 
         [0088]    (2) Optimization of Hydride Vapor Phase Epitaxy (HVPE) growth for (Al,In,Ga)N heterostructures with a thin (400 nm) Al x Ga 1-x N etch stop layer where 0.1&lt;x&lt;0.5. 
         [0089]    (3) Optimization of ICP conditions to maximize etch selectivity between (Al,In,Ga)N heterostructures. 
         [0090]    (4) Optimization of ICP conditions to minimize etch damage to a (Al,In,Ga)N hetero structures. 
         [0091]    (5) Optimization of ICP conditions to minimize the roughness of the etch surface. Nomenclature 
         [0092]    The terms “(Al,In,Ga)N”, “III-nitride”, “Group-III nitride”, or “nitride,” or GaN, AlGaN, InGaN or AlInGaN, as used herein refer to any alloy composition of the (Al,In,Ga)N semiconductors having the formula Al x In y Ga z N where 0≦x≦1, 0≦y≦1, 0≦z≦1, and x+y+z=1. These terms are intended to be broadly construed to include respective nitrides of the single species, Al, In and Ga, as well as binary, ternary and quaternary compositions of such Group III metal species. Accordingly, it will be appreciated that the discussion of the invention hereinafter in reference to GaN, AlGaN and InGaN materials is applicable to the formation of various other (Al,In,Ga)N material species. Further, (Al,In,Ga)N materials within the scope of the invention may further include minor quantities of dopants and/or other impurity or inclusional materials. 
       REFERENCES 
       [0093]    The following references are incorporated by reference herein:
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       CONCLUSION 
       [0113]    This concludes the description of the preferred embodiments 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 claims appended hereto.