Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 41: Nitrides: InGaN
HL 41.1: Talk
Tuesday, March 15, 2011, 14:15–14:30, POT 51
Systematics of nonradiative recombination in blue and green emitting GaInN/GaN quantum wells — •Torsten Langer, Andreas Kruse, Markus Göthlich, Holger Jönen, Heiko Bremers, Uwe Rossow, and Andreas Hangleiter — Institut für Angewandte Physik, Technische Universität Braunschweig
Light emitters based on GaInN/GaN quantum wells (QW) exhibit a strong drop of efficiency for increasing peak emission wavelengths known as “green gap”. In this contribution, we analyze its origin by temperature dependent time-resolved photoluminescence spectroscopy, separating non-radiative and radiative contributions to the carrier recombination processes. We control the peak emission wavelength by varying the indium mole fraction xIn between 18% and 38%. The QW thickness is kept below 2 nm to reduce both the risk of lattice relaxation and the diminishing influence of piezoelectric fields on the oscillator strength (especially for c-plane QWs). While the influence of piezoelectric fields is experimentally observed by an increase of radiative lifetimes towards higher xIn and thicker QWs, a strong reduction of nonradiative lifetimes τnr occurs for high xIn (> 25%). As the experiments were performed in the low carrier density regime, the nonradiative recombination rate Rnr∝ 1/τnr is of defect-related nature following an exponential temperature dependence Rnr∝ exp( − E/(kT) ) with an activation energy E. We compare the lifetimes of uncapped multi quantum well (MQW) structures with efficiency optimized structures as well as samples grown on different substrates: sapphire and HVPE-grown pseudo-bulk GaN.