Optimization of a -plane (112¯0) InN grown via MOVPE on a-plane GaN buffer layers on r -plane (11¯02) sapphire

We have performed a comprehensive investigation of the growth parameter space for the MOVPE of a  -plane (112¯0) InN on a-plane GaN buffer layers deposited on r  -plane (11¯02) sapphire substrates. About 0.2μm thick a  -plane InN epilayers were grown on 1μm thick a-plane GaN buffer layers in a close-coupled 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 in-plane mosaicity. The (112¯0)ω-fwhmω-fwhm varies depending on the scattering vector being parallel to the c-direction 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 T=550 °C, P=500 Torr, V/III = 11,000, where the ω-fwhmω-fwhm for symmetric (112¯0) reflections are 0.83° and 1.04° along [0 0 0 1] and [11¯00] directions, respectively, and for the skew-symmetric (101¯1) plane is 1.47°. 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 cm2/V s, carrier concentration 1.4×1019 cm−3 at room temperature.