Temperature dependence of strain in AlxGa1-xN/GaN heterostructures

The temperature dependence of strain in a 50-nm- and a 100-nm-thick Al_0.2Ga_0.8N/GaN heterostructures were investigated at temperatures 300-800 K. The results show that the temperature behavior of the in-plane strain in the 50-nm-thick AlGaN layer is different to that in the 100-nm-thick AlGaN layer. There exists an initial energy barrier to the strain relaxation for the 50-nm-thick Al_0.22Ga_0.78N/GaN heterostructure. Meanwhile, for both the 50-nm-and 100-nm-thick AlGaN layers the strain relaxation becomes saturated at the high temperature segment, although the temperature at the point of saturation is different. The total strain relaxation is less than 5% for both the 50-nm- and 100-nm-thick Al_0.22Ga_0.78N layers at whole temperature range in our measurements.