Metalorganic Vapor Phase Epitaxy System Research Articles

Beyond ab initio reaction simulator: An application to GaN metalorganic vapor phase epitaxy

To develop a quantitative reaction simulator, data assimilation was performed using high-resolution time-of-flight mass spectrometry (TOF-MS) data applied to a GaN metalorganic vapor phase epitaxy system. Incorporating ab initio knowledge into the optimization enables it to reproduce not only the concentration of CH4 (an impurity precursor) as an objective variable but also known reaction pathways. The simulation results show significant production of GaH3, a precursor of GaN, which has been difficult to detect in TOF-MS experiments. Our proposed approach is expected to be applicable to other applied physics fields that require quantitative prediction that goes beyond ab initio reaction rates.

Coherent Hole Transport in Selective Area Grown Ge Nanowire Networks.

Holes in germanium nanowires have emerged as a realistic platform for quantum computing based on spin qubit logic. On top of the large spin–orbit coupling that allows fast qubit operation, nanowire geometry and orientation can be tuned to cancel out charge noise and hyperfine interaction. Here, we demonstrate a scalable approach to synthesize and organize Ge nanowires on silicon (100)-oriented substrates. Germanium nanowire networks are obtained by selectively growing on nanopatterned slits in a metalorganic vapor phase epitaxy system. Low-temperature electronic transport measurements are performed on nanowire Hall bar devices revealing high hole doping of ∼1018 cm–3 and mean free path of ∼10 nm. Quantum diffusive transport phenomena, universal conductance fluctuations, and weak antilocalization are revealed through magneto transport measurements yielding a coherence and a spin–orbit length of the order of 100 and 10 nm, respectively.

Raman spectra of semi-polar (11-22) InGaN thick films

We report the semi-polar (11-22) InGaN thick films (∼1 μm) grown on m-plane sapphire by a low pressure metal-organic vapor phase epitaxy (MOVPE) system. The Raman spectra of semi-polar InGaN thick films have been studied. For Raman spectra excited by the laser with wavelength of 532 nm, the E2(h) modes of GaN around 569 cm−1 and longitudinal optical (LO) phonon-plasma coupled modes (LPP) were mainly discussed. The E2(h) mode of GaN in the InGaN thick film would correspond to the lower frequency with wavenumber of 569.1 cm−1, compared to that in the InGaN thinner film (569.6 cm-1) in our case. Meanwhile, LPP modes also exhibited red shift with the increase of InGaN film thickness, which would be attributed to the stress relaxation and the decrease of free carrier concentration. The E2(h) modes of InGaN around 560 to 565 cm-1 and A1(LO) modes of InGaN around 729 to 731 cm-1 were found in Raman spectra excited by the laser with wavelength of 325 nm, but not probed in Raman spectra excited by a 532 nm laser. With the increase of In component, both modes were shifted towards low frequency. In addition, it was found that the Frölich electron-phonon interaction would significantly affect the peak position (729.2 cm-1) and full width at half maximum (FWHM, 17.2 cm-1) of A1(LO) mode of InGaN in the thicker film. Moreover, we have compared the Raman spectra of polar and semi-polar InGaN thick films so that the difference of Raman spectra between the two counterparts could be indicated due to lattice mismatch, In component incorporation efficiency, crystal quality and phase separation. The stress distribution of semi-polar InGaN materials is not as uniform as that of polar materials.

In situ passivation of Ga x In(1−x)P nanowires using radial Al y In(1−y)P shells grown by MOVPE

Ga x In(1−x)P nanowires with suitable bandgap (1.35–2.26 eV) ranging from the visible to near-infrared wavelength have great potential in optoelectronic applications. Due to the large surface-to-volume ratio of nanowires, the surface states become a pronounced factor affecting device performance. In this work, we performed a systematic study of Ga x In(1−x)P nanowires’ surface passivation, utilizing Al y In(1−y)P shells grown in situ by using a metal-organic vapor phase epitaxy system. Time-resolved photoinduced luminescence and time-resolved THz spectroscopy measurements were performed to study the nanowires’ carrier recombination processes. Compared to the bare Ga0.41In0.59P nanowires without shells, the hole and electron lifetime of the nanowires with the Al0.36In0.64P shells are found to be larger by 40 and 1.1 times, respectively, demonstrating effective surface passivation of trap states. When shells with higher Al composition were grown, both lifetimes of free holes and electrons decreased prominently. We attribute the acceleration of PL decay to an increase in the trap states’ density due to the formation of defects, including the polycrystalline and oxidized amorphous areas in these samples. Furthermore, in a separate set of samples, we varied the shell thickness. We observed that a certain shell thickness of approximately ∼20 nm is needed for efficient passivation of Ga0.31In0.69P nanowires. The photoconductivity of the sample with a shell thickness of 23 nm decays 10 times slower compared with that of the bare core nanowires. We concluded that both the hole and electron trapping and the overall charge recombination in Ga x In(1−x)P nanowires can be substantially passivated through growing an Al y In(1−y)P shell with appropriate Al composition and thickness. Therefore, we have developed an effective in situ surface passivation of Ga x In(1−x)P nanowires by use of Al y In(1−y)P shells, paving the way to high-performance Ga x In(1−x)P nanowires optoelectronic devices.

In situ analysis of Bi terminated GaAs (0 0 1) and Ga(As,Bi) surfaces during growth by MOVPE

The influence of trimethylbismuth (TMBi) on the GaAs (001) surface reconstruction is studied in situ by reflection anisotropy spectroscopy (RAS) in a metal organic vapor phase epitaxy (MOVPE) system. During supply of TMBi the RAS spectra indicate a change of the arsenic rich c(4 × 4)β surface reconstruction to a bismuth terminated surface reconstruction. This Bi terminated surface is correlated to the current understanding of growth mechanisms for III/V semiconductors containing small amounts of bismuth. The formation, thermal stability and influence of the ambient conditions on this surface is analyzed. The RAS results are correlated to mass spectrometric studies with a real time fast Fourier transform quadrupole ion trap mass spectrometer (iTrap), which is used inline in the same MOVPE system. Both results indicate an about 40 °C lower decomposition temperature of TMBi compared to TBAs. The decomposition temperatures are determined by mass spectrometry with 290 °C for TMBi and 330 °C for TBAs. Furthermore, the surface reconstruction is studied during growth of Ga(As,Bi) bulk layers grown on GaAs. Under ideal conditions, the RAS measurement of the Ga(As,Bi) growth surface shows the signal of a c(4 × 4)β surface reconstruction which is shifted to lower energies as compared to the GaAs surface reconstruction.

Dependence of the V/III Ratio on Indium Incorporation in InGaN Films Grown by Metalorganic Vapour Phase Epitaxy.

InGaN epitaxial layers were grown on c-plane sapphire substrates using the metalorganic vapour phase epitaxy (MOVPE) system at 760 °C. By varying the total flow rate of group-III sources (TMI+TEG) with a fixed molar ratio of group-III sources [TMI/(TMI+TEG)], the influence of V/III ratio were investigated from 4500 to 20000. The grown N-polar InGaN layers were investigated by atomic force microscopy and it is found that the surface roughness decreases with increasing the V/III ratios. High resolution X-ray diffraction analyses show that the phase separation decreases with increasing the V/III ratios. Photoluminescence measurements reveal that the peak position of the band-edge emission shifted toward the shorter wavelength with increasing the V/III ratios. Reciprocal space mapping (RSM) analyses were carried out on InGaN films. At low V/III ratio, the phase separation can be detected in InGaN films.

An experimental approach for real time mass spectrometric CVD gas phase investigations

This is a report on the first setup of a recently developed, extremely sensitive and very fast 3D quadrupole ion trap mass spectrometer inline in a metalorganic vapour phase epitaxy (MOVPE) system. This setup was developed ultimately for the decomposition- and the interaction analysis of various established as well as novel metalorganic sources for MOVPE deposition of III/V semiconductors. To make in-situ gas phase and growth interaction analysis on a new level of sensitivity possible without disturbing the MOVPE growth process itself, an optimized experimental connection of the mass spectrometer to the MOVPE system is required. This work reports on the realization of such an experimental setup and provides first proof of concept for decomposition analysis. In addition, a comparison to previous studies and gas-phase analysis at MOVPE systems will be given in this work.

Metalorganic vapor phase epitaxy of AlN on sapphire with low etch pit density

Using metalorganic vapor phase epitaxy, methods were developed to achieve AlN films on sapphire with low etch pit density (EPD). Key to this achievement was using the same AlN growth recipe and only varying the pre-growth conditioning of the quartz-ware. After AlN growth, the quartz-ware was removed from the growth chamber and either exposed to room air or moved into the N2 purged glove box and exposed to H2O vapor. After the quartz-ware was exposed to room air or H2O, the AlN film growth was found to be more reproducible, resulting in films with (0002) and (10–12) x-ray diffraction (XRD) rocking curve linewidths of 200 and 500 arc sec, respectively, and EPDs < 100 cm−2. The EPD was found to correlate with (0002) linewidths, suggesting that the etch pits are associated with open core screw dislocations similar to GaN films. Once reproducible AlN conditions were established using the H2O pre-treatment, it was found that even small doses of trimethylaluminum (TMAl)/NH3 on the quartz-ware surfaces generated AlN films with higher EPDs. The presence of these residual TMAl/NH3-derived coatings in metalorganic vapor phase epitaxy (MOVPE) systems and their impact on the sapphire surface during heating might explain why reproducible growth of AlN on sapphire is difficult.

Annealing of Au, Ag and Au–Ag alloy nanoparticle arrays on GaAs (100) and (111)B

Metal nanoparticles (NPs), in particular gold NPs, are often used in the fabrication process of semiconductor nanowires. Besides being able to induce the 1D crystallization of new material, it is highly beneficial if the NPs can be used to dictate the position and diameter of the final nanowire structure. To achieve well-defined NP arrays of varying diameter and pitch distances for nanowire growth, it is necessary to understand and control the effect that a pre-growth annealing process may have on the pre-defined NP arrays. Recently, it has been demonstrated that silver (Ag) may be an alternative to using gold (Au) NPs as seed for particle-seeded nanowire fabrication. This work brings light onto the effect of annealing of Au, Ag and Au–Ag alloy metal NP arrays in two commonly used epitaxial systems, the molecular beam epitaxy (MBE) and the metalorganic vapor phase epitaxy (MOVPE). The metal NP arrays are fabricated with the aid of electron beam lithography on GaAs 100 and 111B wafers and the evolution of the NPs with respect to shape, size and position on the surfaces is studied after annealing using scanning electron microscopy. We find that while the Au NP arrays are found to be stable when annealed up to 600 °C in a MOVPE system, a diameter and pitch dependent splitting of the particles is seen for annealing in a MBE system. The Ag NP arrays are found to be less stable, with smaller diameters (≤50 nm) dissolving during the annealing process in both epitaxial systems. In general, the mobility of the NPs is observed to differ between the two the GaAs 100 and 111B surfaces. Finally, our observations on the effect of annealing on Au–Ag alloy NP arrays suggest that these NP can withstand necessary annealing conditions for a complete de-oxidation of GaAs surfaces in both MOVPE and MBE.

New photocathode using ZnSe substrates with GaAs active layer

GaAs active layers were successfully fabricated on ZnSe substrates using a metalorganic vapor phase epitaxy system. As a photocathode, a GaAs active layer shows a high quantum efficiency (QE) of 9% at 532 nm laser light illumination, which is comparable to a QE of 11% from GaAs bulk. In addition, a photoemission current of 10 µA was obtained from this photocathode. One more important point is that this photocathode could realize back-side illumination of 532 nm laser light, and thus its widespread applications are expected in microscopy and accelerator fields.

Lithography-free shell-substrate isolation for core–shell GaAs nanowires

A facile and scalable lithography-free technique for the rapid construction of GaAs core–shell nanowires incorporating shell isolation from the substrate is reported. The process is based on interrupting NW growth and applying a thin spin-on-glass (SOG) layer to the base of the NWs and resuming core–shell NW growth. NW growth occurred in an atmospheric pressure metalorganic vapour phase epitaxy (MOVPE) system with gold nanoparticles used as catalysts for the vapour−liquid−solid growth. It is shown that NW axial core growth and radial shell growth can be resumed after interruption and even exposure to air. The SOG residues and native oxide layer that forms on the NW surface are shown to prevent or perturb resumption of epitaxial NW growth if not removed. Both HF etching and in situ annealing of the air-exposed NWs in the MOVPE were shown to remove the SOG residues and native oxide layer. While both procedures are shown capable of removing the native oxide and enabling resumption of epitaxial NW growth, in situ annealing produced the best results and allowed construction of pristine core–shell NWs. No growth occurred on SOG and it was observed that axial NW growth was more rapid when a SOG layer covered the substrate. The fabricated p-core/n-shell NWs exhibited diode behaviour upon electrical testing. The isolation of the NW shells from the substrate was confirmed by scanning electron microscopy and electrical measurements. The crystal quality of the regrown core–shell NWs was verified with a high resolution transmission electron microscope. The reported technique potentially provides a pathway using MOVPE for scalable and high-throughput production of shell-substrate isolated core–shell NWs on an industrial scale.

Vertical GaN p-n Junction Diodes With High Breakdown Voltages Over 4 kV

Vertical structured GaN power devices have recently been attracting a great interest because of their potential on extremely high-power conversion efficiency. This letter describes increased breakdown voltages in the vertical GaN p-n diodes fabricated on the free-standing GaN substrates. By applying multiple lightly Si doped n-GaN drift layers to the p-n diode, the record breakdown voltages (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> ) of 4.7 kV combined with low specific differential ON-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ) of 1.7 mΩcm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> were achieved. With reducing the Si-doping concentration of the top n-GaN drift layer adjacent to the p-n junction using well-controlled metal-organic vapor phase epitaxy systems, the peak electric field at the p-n junction could be suppressed under high negatively biased conditions. The second drift layer with a moderate doping concentration contributed to the low R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> . A Baliga's figure of merit (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ) was 13 GW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . These are the best values ever reported among those achieved by GaN p-n junction diodes on the free-standing GaN substrates.

Investigations on Al$_{\bm x}$Ga$_{\bm {1-x}}$As Solar Cells Grown by MOVPE

Solar cells based on Al x Ga 1-x As in its direct bandgap range were fabricated and analyzed. We show that state-of-the-art metalorganic vapor phase epitaxy systems and precursors are capable of growing Al x Ga 1-x As solar cells with defect concentrations up to 1 × 10 14 cm -3 and less determined by deep level transient spectroscopy. However, for the n-doped material, inevitable DX-centers exist. These dopant-related defects limit the performance of the investigated Al x Ga 1-x As solar cells with x ≥ 0.20. To overcome this issue, the n-doped Al x Ga 1-x As As emitter can be replaced by an n-doped Ga 0.51 In 0.49 P heteroemitter. This heterojunction solar cell again shows overall defect concentrations below 1 × 10 14 cm -3 and significantly improved cell characteristics.

In situ X-ray Reflectivity Measurements on Annealed InxGa1-xN Epilayer Grown by Metalorganic Vapor Phase Epitaxy

The thermal decomposition of c-plane GaN/sapphire templates was studied in a metalorganic vapor phase epitaxy (MOVPE) system installed in a laboratory-level X-ray diffractometer by using in situ X-ray reflectivity (XRR). GaN remained thermally stable in pure N2 up to 900 °C, while a significant decomposition occurred at 950 °C. Then, thin InxGa1-xN epilayers were grown on the annealed templates at 830 °C. In situ XRR measurements were conducted before and after InGaN growth. By theoretical and experimental analyses of the XRR spectra, the sample structure change upon thermal annealing was clarified. Photoluminecescence (PL) and atomic force microscopy (AFM) results demonstrated that thermal annealing affected the optical properties and microstructures of InGaN films. The PL peaks from InGaN slightly blue-shifted with thermal annealing.

A Comparative Study on Metalorganic Vapor Phase Epitaxial InGaN with Intermediate In Compositions Grown on GaN/Sapphire Template and AlN/Si(111) Substrate

The growth of InGaN with intermediate In compositions on GaN/sapphire template and AlN/Si(111) substrate has been comparatively studied. By using an metalorganic vapor phase epitaxy (MOVPE) system with a horizontal reactor, InGaN films are grown at a temperature of 600–800 °C in the pressure of 150 Torr. By optimizing growth temperature and trimethylindium/(trimethylindium+ triethylgallium) molar ratio, single crystalline InxGa1-xN with x = 0–1 are successfully grown on both substrates. The films grown at a relatively high temperature (≥700 °C) with In compositions of 0.3 or less show phase separation when their thickness exceeds a critical value (0.25–0.4 µm), while the samples grown at 600 °C with In compositions of 0.35–0.5 show no phase separation even if the thickness is increased to 0.7 µm. To evaluate the crystalline quality of grown films, FWHM of X-ray rocking curve (XRC) for InGaN(0002), tilt, is measured. There is no marked difference in tilt data between films grown on GaN/α-Al2O3(0001) and AlN/Si(111). For the samples grown at 600 °C with In contents of 0.35–0.5, tilt data are drastically increased and widely scattered suggesting the existence of important unknown parameters that govern crystalline quality of InGaN grown at a relatively low temperature.

Optical properties of InN films grown by pressurized-reactor metalorganic vapor phase epitaxy

InN thin films have been grown using a pressurized-reactor metalorganic vapor phase epitaxy system at 500–700°C under the pressure of 2.1×105Pa. Photoluminescence (PL), optical reflectance and transmission measurements were performed at room temperature. We found that optical properties of these as-grown films strongly depend on the growth temperature. By analyzing the reflectance spectra, it is found that the calculated carrier concentrations of the films increased with decreasing growth temperature. Room-temperature photoluminescence spectra show that the films grown at temperatures higher than 575°C have strong emission peaks at 0.68–0.75eV, while those grown at temperatures lower than and equal to 575°C have negligible emission. The quenching of the emission is attributed to the existences of cubic InN and a high-density of nonradiative recombination centers in the films grown at low growth temperature region. Especially for the case of high temperature growth, the growth temperature dependence of the absorption-edge energy shows a similar tendency with that of the PL peak energy, both blue-shifted with decreasing the growth temperature possibly due to the well-known Burstein–Moss effects. From these results, an optimum growth temperature of 675°C in the pressurized growth could be obtained.

High-growth-rate AlGaN buffer layers and atmospheric-pressure growth of low-carbon GaN for AlGaN/GaN HEMT on the 6-in.-diameter Si substrate metal-organic vapor phase epitaxy system

In this study, we investigated the effects of growth pressure on incorporation of carbon in GaN and on the growth rate of AlGaN using a multiwafer (7×6in.) mass-production metal-organic vapor phase epitaxy (MOVPE) reactor. In the two-dimensional electron gas (2DEG) region of an AlGaN/GaN high electron-mobility transistor (HEMT) structure, a high GaN purity is required. The incorporation of carbon in GaN could be easily controlled over a carbon concentration range of three orders of magnitude by varying pressure. Thus, the reactor can be used for growth at both reduced pressure and atmospheric pressure. Furthermore, an AlGaN growth rate of over 1μm/h was demonstrated for Al composition in the range of 0.3–0.8 by suppressing the gas-phase prereaction between the precursor materials. An AlGaN/GaN HEMT structure was also demonstrated. The magnitude of wafer bowing was less than 50μm. The full widths at half maximum (FWHMs) of the X-ray rocking curve (XRC) of GaN were 570″ in the GaN (002) direction and 760″ in the GaN (102) direction. The sheet carrier density and Hall mobility were 1.056×1013cm−2 and 1550cm2/Vs, respectively.

Characterization of the post-thermal annealing effect for p-GaAs/i-InGaAsN/n-GaAs hetero-junction solar cells

In this study, we demonstrated the fabrication and characterization of p-GaAs/i-InGaAsN/n-GaAs double hetero-junction solar cells (DHJSCs). The intrinsic InGaAsN absorption layer which is lattice-matched with GaAs substrates was grown by the metal-organic vapor phase epitaxy (MOVPE) system. The metal-organic sources used in the MOVPE growth induced unintentionally-doped carbon adatoms, and this in turn caused some carbon-related defects. This carbon pollution subsequently deteriorated the optical and electrical characteristics of the dilute nitride material. With ex-situ post-annealing being carried out in the furnace, it could not only modify the crystallinity of the InGaAsN material, but the deterioration in the performance of the dilute nitride solar cell due to the nitrogen incorporation could also be mitigated. After conducting the thermal annealing at 550°C for 1h in nitrogen ambience, the conversion efficiency of the DHJSCs was increased from 0.61% to 4.46% under Air Mass 1.5 Global (1000W/m2, AM1.5G) irradiance. The external quantum efficiency (EQE) spectrum further revealed that the efficiency of DHJSCs had been enhanced significantly owing to the crystalline improvement of the intrinsic InGaAsN absorption layer after the ex-situ post-thermal annealing was implemented. This improvement also led to a significant increase in the short-circuit current. The X-ray photoelectron spectroscopy (XPS) measurement result also showed that the ex-situ thermal annealing contributed to the improvement of crystal quality and the reduction of carbon related defects and clusters in the as-grown InGaAsN absorption layer.

Optical characterization of a GaAsSb/GaAs/GaAsP strain-compensated quantum well structure grown by metal-organic vapor phase epitaxy

Optical properties of a strained GaAs0.64Sb0.36/GaAs and a strain-compensated GaAs0.64Sb0.36/GaAs/GaAs0.79P0.21 triple quantum well (TQW) structures were investigated by photoluminescence (PL), photoreflectance (PR) and surface photovoltage spectroscopy (SPS). The samples were grown on GaAs(100) substrates by a horizontal metal-organic vapor phase epitaxy (MOVPE) system. For GaAs0.64Sb0.36/GaAs TQW, a large blueshift of the peak position of PL feature at low temperature with increasing excitation power density and only a very weak PR feature observed in the vicinity of fundamental transitions and were attributed to a weakly type-II heterojunction formed between GaAs0.64Sb0.36 and GaAs. On the other hand, the PR and SPS spectra of GaAs0.64Sb0.36/GaAs/GaAs0.79P0.21 TQW showed a series of intersubband originated transition features, which is a typical characteristic of type-I QW structure. The results revealed that the energy band of QW structures is significantly influenced by the inserted tensile GaAsP layers, which changes the weakly type-II to a type-I structure. The strain-compensated GaAs0.64Sb0.36/GaAs/GaAs0.79P0.21 TQW has a larger overlap integral and hence a higher transition probability, providing a possibility for fabricating high efficiency near infrared laser diodes.

Phase diagram on phase purity of InN grown pressurized‐reactor MOVPE

AbstractInN epitaxial films are directly grown on sapphire (0001) substrates by using Pressurised‐Reactor metalorganic vapour phase epitaxy (PR‐MOVPE) system originally developed by ourselves. This system makes it possible to control the side wall of islands perpendicular to the substrate surface, which is important in the heteroepitaxial growth with large lattice‐mismatch from the analogy of the GaN growth on sapphire substrates. This high pressure also leads to the growth at the higher temperature than that at the atmospheric pressure. In this paper, InN films are grown by PR‐MOVPE at 2,400 Torr. Its polarity is nitrogen one, which has the superior efficiency to indium polarity in the capture of nitrogen at the growth front. To crystallographically identify films using the diffractions from sapphire (006), wurtzite (WZ) InN (002), zincblende (ZB) InN (111) and metallic indium (101), 2θ–ω scans and the pole figure measurements in X‐ray diffraction are measured. From the pole figure measurements, the orientation and crystalline phases of grains in crystals are determined. The phase diagram between trimethylindium as an indium source flow rate and the growth temperature is drawn. The regions with pure WZ InN and with the incorporation of ZB phase and the metallic indium into WZ phase and the metal‐indium are observed. It is also observed that the grains with WZ phase have c‐axis normal to the (111) plane at the side wall of the ZB grains. Finally, the growth conditions for pure WZ InN make it clear by using PR‐MOVPE. (© 2012 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)