Investigation of unintentional indium incorporation into GaN barriers of InGaN/GaN quantum well structures

High resolution transmission electron microscopy has been employed to investigate the impact of the GaN bar-rier growth technique on the composition profile of InGaN quantum wells (QWs). We show that the profiles deviate from their nominal configuration due to the pres-ence of an indium tail at the upper interface of the QW. This indium tail, thought to be associated with a segrega-tion effect from the indium surfactant layer, has been shown to strongly depend on the growth method. The ef-fect of this tail has been investigated using a self-consistent Schrödinger-Poisson simulation. For the simu-lated conditions, a graded upper interface has been found to result in a decreased electron-hole wavefunction over-lap of up to 31 % compared to a QW with a rectangular profile, possibly leading to a decrease in radiative-recombination rate. Therefore in order to maximize the efficiency of a QW structure, it is important to grow the active region using a growth method which leads to QW interfaces which are as abrupt as possible. The results of this experiment find applications in every study where the emission properties of a device are correlated to a particular active region design.