Stability and interface abruptness of InxGa1?xN/InyGa1?yN multiple quantum well structures grown by OMVPE

The abruptness of hetero-interfaces in InGaN multiple quantum well structures is shown to degrade when a high temperature growth follows growth of the multiple quantum well (MQW) region, as is generally required for the growth of full device structures. We have analyzed MQW samples both with and without high temperature GaN “cap” layers, using x-ray diffraction (XRD), grazing incidence x-ray reflection (GIXR), and photoluminescence. While all of these techniques indicate a degradation of the MQW structure when it is followed by growth at high temperature, GIXR is shown to be especially sensitive to changes of heterointerface abruptness. GIXR measurements indicate that the heterojunctions are less abrupt in samples that have high temperature cap layers, as compared to samples with no cap layer. Furthermore, the degree of roughening is found to increase with the duration of growth of the high temperature cap layer. The degradation of the heterointerfaces is also accompanied by a reduction in the intensity of satellite peaks in the x-ray diffraction spectrum.