ScAlMgO4 (SCAM) (0001) can be used for metalorganic vapor phase epitaxy (MOVPE) of GaN and lattice-matched In0.17Ga0.83N. GaN grown on SCAM(0001) via a low-temperature GaN buffer layer shows excellent structural quality, indicating that the GaN-SCAM interface is stable during MOVPE. For lattice-matched InGaN on SCAM(0001), a lattice-matched InGaN buffer layer grown at a lower temperature effectively improves the surface and luminescence uniformity. The grown InGaN is nearly unstrained and exhibits photoluminescence peaking at 505 nm at room temperature. These achievements indicate that In0.17Ga0.83N/SCAM lattice-matched templates may pave the way toward longer-wavelength light-emitting and -detecting devices using InGaN with higher In contents.

We investigate anisotropic lattice relaxation in non-c-plane InGaN/GaN multiple quantum wells (MQWs). Transmission electron microscopy analyses of semipolar ð11 22Þ MQWs reveal that lattice relaxation preferentially occurs along the ½ 1 123 direction by introducing misfit dislocations (MDs) with a Burgers vector of 1 = 3 ½11 20. To theoretically describe this anisotropic relaxation phenomenon, we expand the force-balance model, where the competition between the force induced by lattice mismatch and the tension of dislocations determines the motion of dislocations. Furthermore, because MDs are introduced at the interface between the bottom InGaN QW and the underlying GaN, we propose to treat InGaN/GaN MQWs as InGaN single layers with effective In compositions. Applying this structure model to the theoretical calculation of the critical layer thicknesses reproduces well the experimentally observed lattice relaxation. This achievement enables us to design semipolar InGaN/GaN MQW structures without lattice relaxation, thereby realizing higher internal emission quantum efficiencies. V

We studied hole generation in Mg-doped AlN/Al 0.75 Ga 0.25 N superlattices (SLs) with an average Al content of 0.8. High hole concentrations on the order of 10 18 cm %3 were obtained in the SLs. The temperature dependence of the hole concentration indicated an effective acceptor ionization energy of 40-67 meV, which is much lower than that of Mg-doped Al 0.8 Ga 0.2 N alloy (>400 meV). The hole concentration increased with increasing SL period thickness and became almost constant at about 30 nm. These results indicate that the band bending caused by strong spontaneous and piezoelectric polarization fields enhances the ionization of the Mg acceptors.

We compare metalorganic vapor phase epitaxy of InGaN/GaN heterostructures on semipolar (112¯2) and (1¯1¯22¯) GaN bulk substrates. In incorporation efficiency is higher for (112¯2) InGaN, which enables higher temperature growth of InGaN and is beneficial for quality improvement. InGaN/GaN quantum wells (QWs) on (112¯2) show abrupt interfaces, but those on (1¯1¯22¯) tend to form three-dimensional nanofacets. Differences in growth temperature and structures of the (112¯2) and (1¯1¯22¯) QWs cause higher internal quantum efficiencies of the (112¯2) [(1¯1¯22¯)] QWs at shorter (longer) wavelengths.

We investigate the surface morphologies of nonpolar m‐plane AlN homoepitaxial layers grown by flow‐rate modulation epitaxy (FME). As source supply sequences, we employ a continuous supply and three types of FME: group‐III‐source FME, group‐V‐source FME, and FME with groups III and V alternated. We reveal that the average V/III ratio affects the step‐flow velocity in +c‐ and a‐directions, which determines step direction. In addition, steps toward the +c‐direction tend to bunch under N‐poor conditions. This is probably due to enhanced adatom migration resulting from the FME technique. Thus, we can control the surface morphologies of m‐plane AlN homoepitaxial layers and thereby obtain a flat surface with well‐aligned steps.