HIGH-RESOLUTION X-RAY-ANALYSIS OF INGAN GAN SUPERLATTICES GROWN ON SAPPHIRE SUBSTRATES WITH GAN LAYERS/

InGaN/GaN superlattice structures grown on (0001) sapphire substrates with GaN layers were investigated by two-dimensional reciprocal space mapping of high-resolution x-ray diffraction. The results show that In GaN/GaN multi-quantum wells with fairly good crystallinity can be grow n coherently on partially relaxed GaN layer irrespective of the large lattice mismatch and thermal incompatibility with the underlying subst rate. Narrow and bright band edge related emissions were observed by p hotoluminescence measurements, indicating high quality of these InGaN/ GaN superlattice structures, Our results suggest a larger band-gap bow ing coefficient than the value reported in the literature. (C) 1996 Am erican Institute of Physics.