The direct evidence of the composition pulling effect and its role in InGaN multiple quantum wells

Abstract

Direct evidence of composition pulling effect (CPE) in InGaN` quantum wells was obtained by combining energy dispersive x-ray spectrometry (EDS) and scanning tunneling electron microscope (STEM). The indium content increases along the c-axis in the InGaN quantum wells, forming an In-rich sublayer on the surface. The indium content in the In-rich sublayer will reach saturation earlier. After that, the incorporation of indium atoms is hindered, resulting in a decrease in the average indium composition in the InGaN quantum wells. Moreover, an aggregation behavior of indium atoms has been observed in samples with a stronger CPE. This leads to a lot of dark spot defects, seriously deteriorating the luminescence quality. By restricting the migration ability of indium atoms, dark spot defects could be greatly suppressed, and a higher quality InGaN/GaN MQW with higher indium content was obtained.