Non Destructive Evaluation of AlGaN/GaN HEMT structure by cathodoluminescence spectroscopy

We have investigated radiative defects in various component layers in an AlGaN/GaN HEMT structure by measuring Cathodoluminescence (CL) spectrum as a function of accelerating voltage. Low electron beam accelerating voltages (below 1 kV) CL spectra are used to get information about defects in the cap layer and the barrier layer. Samples with good quality GaN cap layer showed surface quantum well (SQW) transition in the CL spectrum. The cap layer thickness and its quality can be determined from the SQW emission energy and its integrated intensity. We show that low intensity electron beam provides information about the defects in the cap layer as well as barrier layer through the intensity and energy of the yellow luminescence peak. The observed changes in the CL intensity of the barrier layer towards the surface have been correlated to the formation of aluminium oxide, giving rise to higher concentration of deep acceptor defects probably related to the adsorbed oxygen on the uncapped AlGaN barrier layer samples. The results are supported by X-ray photoelectron spectroscopy (XPS), High resolution X-ray diffraction (HRXRD) and Secondary ion mass spectrometry (SIMS) techniques.

Automated summary

Radiative defects in various component layers in an AlGaN/GaN HEMT structure were investigated using Cathodoluminescence (CL) spectrum measurements as a function of accelerating voltage. Low electron beam accelerating voltages provided information about defects in the cap layer and the barrier layer, with features such as surface quantum well (SQW) transitions revealing cap layer thickness and quality. The observed changes in CL intensity of the barrier layer were correlated to the formation of aluminium oxide, resulting in higher concentration of deep acceptor defects likely related to adsorbed oxygen on uncapped AlGaN barrier layer samples.