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%.
Bibliographical noteFunding Information:
This present research was supported by 2016 Hongik University Research Fund and the Basic Science Research Programs through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (2014R1A1A4A01008877).
© 2017 Elsevier B.V.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physics and Astronomy(all)