Growth and characterization of single InGaN quantum well in nonpolar a-plane (112¯0) InGaN/GaN light-emitting diodes

We studied the In incorporation efficiency and composition distribution in a nonpolar a-plane InGaN (a-InGaN) quantum well (QW) layer. The In compositions decreased with increasing growth temperatures due to increased In desorption from InGaN surfaces. It was clear that the In incorporation efficiency on a nonpolar GaN surface is lower than that on a polar c-plane GaN. In addition, the In incorporation rate on an a-InGaN layer could be increased by decreasing the V/III ratio without lowering the growth temperature. In the case of the a-InGaN layer, a composition pulling effect was also observed, suggesting that the In composition of the a-InGaN layer increases along the normal growth direction from the bottom to the top of the InGaN QW layer. Using high-resolution XRD 2θ-ω scans, we found that there existed convex graded In compositions ranging from 4 to 12.7% in an a-InGaN QW layer along the growth direction. No wavelength shift with a current injection of 20-100 mA confirmed the absence of a polarization field. The shift in the electroluminescence (EL) peak energy was ∼11 meV between the electric field parallel and perpendicular to the c-axis components, which was caused by the valence band splitting due to the in-plane compressive strain of the 10 nm a-InGaN QW layer. The EL polarization anisotropy was clearly observed with a polarization ratio of 55%.