Photoluminescence Study of Carrier Localization and Recombination in Nearly Strain‐Balanced Nonpolar InGaN/AlGaN Quantum Wells

Abstract

Temperature‐dependent continuous‐excitation and time‐resolved photoluminescence are studied to probe carrier localization and recombination in nearly strain‐balanced m‐plane In0.09Ga0.91N/Al0.19Ga0.81N multi‐quantum wells grown by plasma‐assisted molecular‐beam epitaxy. An average localization depth of 21 meV is estimated for the undoped sample. This depth is much smaller than the reported values in polar structures and m‐plane InGaN quantum wells. As part of this study, temperature and magnetic field dependence of time‐resolved photoluminescence is performed. At 2 K, an initial fast decay time of ≈0.3 ns is measured for both undoped and doped structures. The undoped sample also exhibits a slow decay component with a time scale of 2.2 ns. The existence of two relaxation paths in the undoped structure can be attributed to different localization centers. The fast relaxation decays are relatively insensitive to external magnetic fields, while the slower relaxation time constant decreases significantly with increasing magnetic fields. The fast decay time scale in the undoped sample is likely due to indium fluctuations in the quantum well. The slow decay time may be related to carrier localization in the barriers. The addition of doping leads to a single fast decay time likely due to stronger exciton localization in the InGaN quantum wells.

Disentangling the Impact of Point Defect Density and Carrier Localization-Enhanced Auger Recombination on Efficiency Droop in (In,Ga)N/GaN Quantum Wells

“…Each sample is labeled by its growth temperature in °C. wurtzite 28 or zincblende GaN 29 have sub-nanosecond recombination lifetimes rather than lifetimes of 10s or 100s of nanoseconds as typically found for c-plane wurtzite greenemitting QWs. 17 However, no significant reduction in droop has yet been observed in nonpolar QWs 30,31 and droop measurements in zincblende GaN QWs have yet to be reported.…”

“…This may be achieved by utilizing QWs grown along alternate crystal directions or in alternate phases that have lower recombination lifetimes, τ, since N = j τ/ et QW , where t QW is the QW thickness. For instance, QWs produced from m -plane wurtzite or zincblende GaN have sub-nanosecond recombination lifetimes rather than lifetimes of 10s or 100s of nanoseconds as typically found for c -plane wurtzite green-emitting QWs . However, no significant reduction in droop has yet been observed in nonpolar QWs , and droop measurements in zincblende GaN QWs have yet to be reported.…”