Study of excess carrier dynamics in polar, semi‐polar, and non‐polar (In,Ga)N epilayers and QWs

Abstract

We studied carrier recombination and diffusion in GaN/sapphire templates, (In,Ga)N layers, and (In,Ga)N quantum well structures oriented along the polar [0001], semi‐polar [11‐22], and non‐polar [11‐20] orientations by means of light induced transient grating, differential transmission, and photoluminescence optical techniques. We show that the lifetime of excess carriers drops by orders of magnitude when changing the orientation from polar to non‐polar, both in GaN templates and (In,Ga)N layers. We attribute the shorter lifetime to carrier trapping by extended structural defects that are more abundant in non‐polar grown samples. In addition, we observe pronounced carrier localization effects in the semi‐ and non‐polar layers. We show that thick (In,Ga)N layers inherit the properties of the GaN templates. However, the thin quantum well structures show a lower carrier trapping activity. So, a better electrical quality can be assumed as compared to the thick (In,Ga)N layers. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Exciton localization in polar and semipolar (112̅2) In0.2Ga0.8N/GaN multiple quantum wells

“…This field reduction has been theoretically predicted to increase overlap between electron and hole wave-functions resulting in an increased radiative recombination probability, which may enhance the performance of LEDs based on semipolar nitrides. However, this prediction needs to be further confirmed experimentally [3][4][5][6].…”

“…This has been linked to the efficiency droop in the polar QWs. For (112̅ 2) InGaN/GaN QWs, to our best knowledge, only a few studies on the effect of ELZ on radiative recombination lifetimes have been performed by time-resolved photoluminescence for (112̅ 2) QWs [3,5,6]. By measuring the Stokes-shift, Zhang et al [6] have reported that a larger polarization field of polar QWs mainly causes a larger shift than (112̅ 2) QWs.…”