X-ray studies of group III-nitride quantum wells with high quality interfaces

This paper reports an investigation of a variety of (InGa)N/GaN multi-quant um-well (MQW) samples grown by metalorganic vapor phase epitaxy on sapphire substrates. Dynamical scattering theory has been used to simulate the x-ra y diffraction profiles so as to model the structures and to assess the qual ity of the grown interfaces. There is good agreement between the theoretica l predictions and the experimental data. A systematic comparison of a set o f ten-period MQWs with different well widths is also reported together with a discussion of the comparison between a single quantum well (QW) with fiv e- and ten-period MQWs all with the same well and barrier widths and alloy composition. The well and barrier widths deduced from the x-ray measurement s agree within experimental error with those predicted from the growth para meters, however, the In content of the wells appears to be substantially lo wer than that expected. This is discussed in terms of a carbon incorporatio n model. Tn the better samples, the (InGa)N/GaN interface is good to within a few monolayers-this is comparable with the best that can be achieved in (AlGa)As/GaAs QWs. (C) 2000 American Vacuum Society. [S0734-211X(00)08704-7 ].