Optimization of a-plane InN grown via MOVPE on a-plane GaN buffer layers on r-plane sapphire

Abstract

a b s t r a c tWe have performed a comprehensive investigation of the growth parameter space for the MOVPE of aplane ð1 1 2 0Þ InN on a-plane GaN buffer layers deposited on r-plane ð1 1 0 2Þ sapphire substrates. About 0:2 mm thick a-plane InN epilayers were grown on 1 mm thick a-plane GaN buffer layers in a closecoupled showerhead reactor. The growth parameters-substrate temperature, reactor pressure, V/III ratio-were systematically varied and their effect on structural, electrical, optical and morphological properties of a-plane InN films were studied. All a-plane InN epilayers show an anisotropy in the inplane mosaicity. The ð1 1 2 0Þ oÀfwhm varies depending on the scattering vector being parallel to the cdirection or the m-direction. The magnitude and nature of this anisotropy is strongly influenced by the growth parameters. In general compared to c-plane InN, we observed a higher growth rate and a slightly higher optimum growth temperature for the a-plane InN epilayers. The optimum growth conditions are found at T¼ 550 1C, P ¼ 500 Torr, V/III ¼ 11,000, where the oÀfwhm for symmetric ð1 1 2 0Þ reflections are 0.831 and 1.041 along [0 0 0 1] and ½1 1 0 0 directions, respectively, and for the skew-symmetric ð1 0 1 1Þ plane is 1.471. The optimized a-plane InN has a photoluminescence peak emission at 1750 nm (0.71 eV) at low temperature (11 K) and a mobility of 234 cm 2 /V s, carrier concentration 1.4 Â 10 19 cm À 3 at room temperature.

MOCVD growth of a-plane InN films on r-Al2O3 with different buffer layers

“…The anisotropies in a-plane InN were previously reported by Koblmuller et al [22] and Ajagunna et al [10], but in their studies, the anisotropies were negligible compared to m-plane InN and a-plane GaN. Very recently, Laskar et al [23] reported an M-shaped plot of FWHM against azimuth in plane of aplane InN, which is similar to a-plane GaN. In our MOCVD growth, these anisotropies are also significantly beyond negligible.…”

Influence of buffer layers on the microstructure of MOVPE grown a-plane InN

“…Trimethylgallium (TMGa), trimethylaluminium (TMAl), trimethylindium (TMIn) and ammonia (NH 3 ) were used as precursors and getter-purified nitrogen (N 2 ) as carrier gas. Details of the growth procedure can be found in our earlier optimization study [11] from where the best conditions for the growth of a-plane InN were found to be temperature T¼550 1C, pressure P¼500 Torr, and V/III characterization of the InN layers was carried out using a Philips XPERT TM HRXRD system using CuKa 1 X-rays with a hybrid monochromator providing an angular divergence of 18 arcsec in the scattering plane, and the data collected using a 2.51 open PIXcel solid state detector array. Both symmetric ð1 1 2 0Þ, ð2 2 4 0Þ reflections along c-and m-direction and the skew-symmetric ð1 0 1 0Þ, ð2 0 2 0Þ, ð3 0 3 0Þ, and ð1 0 1 1Þ were recorded.…”

“…The epitaxial growth of InN in non-polar directions is much more challenging than growth of c-plane oriented films, because the different growth mechanisms are not well understood. There are few reports of growing a-plane ð1 1 2 0Þ InN by molecular beam epitaxy [8,9] and MOVPE [10,11]. In our previous work [11] we have explored the growth parameter space for a-plane InN in a close-coupled showerhead reactor and optimized the growth conditions for a-plane InN on GaN buffer layer.…”

“…There are few reports of growing a-plane ð1 1 2 0Þ InN by molecular beam epitaxy [8,9] and MOVPE [10,11]. In our previous work [11] we have explored the growth parameter space for a-plane InN in a close-coupled showerhead reactor and optimized the growth conditions for a-plane InN on GaN buffer layer. Under those optimized growth condition we have grown a-plane InN on different buffer layers.…”