Evaluation of radiative and non-radiative recombination lifetimes in c-plane InGaN quantum wells with different In composition

Abstract

It is well-known that c-plane InGaN quantum wells (QWs), which are usually used as active layers in optical devices, have a problem that the emission efficiency decreases with the increasing In composition. Two possible origins have been proposed for the main cause of this problem. One is related with piezo-electric field. Large lattice mismatch between the InGaN-QW layer and the underlying GaN layer induces a large piezo-electric field in the QW, causing spatial separation of electrons and holes and reducing radiative recombination probability. The other one is related with defect density. The large lattice mismatch generates many defects and they enhance non-radiative recombination probability. So far, however, there is no clear evidence as to which of the two effects is dominant.
In this work, we have separately evaluated the radiative and non-radiative recombination lifetimes for a series of InGaN-QW samples with different In compositions. The two recombination lifetimes can be obtained from carrier lifetime (estimated by time-resolved photoluminescence (PL) measurement) and internal quantum efficiency (IQE) (estimated by simultaneous photoacoustic (PA) and PL measurement method [1]). Figure 1 shows the estimated two recombination lifetimes in all the samples, and it can be clearly said that the decrease in emission efficiency with increasing In composition is caused by the decrease in radiative recombination probability.