Local carrier recombination and associated dynamics in m-plane InGaN/GaN quantum wells probed by picosecond cathodoluminescence

We report on spatially resolved and time-resolvedcathodoluminescence(CL) studies of the recombination mechanisms of InGaN/GaNquantum wells(QWs) grown by metal-organic vapour phase epitaxy on bulkm-plane AmmonoGaN substrates. As a result of the 2 ° miscut of theGaN substrate, the sample surface exhibits step bunches, where semi-polarQWs with a higherindium concentration than the planarm-planeQWs form during theQW growth. Spatially resolved time-integratedCL maps under both continuous and pulsed excitation show a broad emission band originating from them-planeQWs and a distinct low energy emission originating from the semi-polarQWs at the step bunches. High resolution time-resolvedCL maps reveal that when them-QWs are excited well away from the step bunches the emission from them-planeQWs decays with a time constant of 350 ps, whereas the emission originating semi-polarQWs decays with a longer time constant of 489 ps. The time constant of the decay from the semi-polarQWs is longer due to the separation of the carrierwavefunctions caused by theelectric field across the semi-polarQWs.

Source: Applied Physics Letters - December 5, 2016 Category: Physics Authors: Tongtong Zhu, David Gachet, Fengzai Tang, Wai Yuen Fu, Fabrice Oehler, Menno J. Kappers, Phil Dawson, Colin J. Humphreys and Rachel A. Oliver Source Type: research