Sharp variations in the temperature dependence of optical reflectivity from AlN/GaN heterostructures

Abstract

Sharp variations in optical reflectivity were observed when cooling and heating AlN/GaN heterostructures on sapphire substrates between room temperature and 10 K. The reflectivity was found to decrease at a definite temperature Tk in the downward temperature run, and to recover at Tr > Tk in the subsequent upward temperature run. The temperature behaviour of reflectivity exhibits memory on the cooling–heating cycles previously subjected to samples.