X-ray crystal truncation rod (CTR) scattering technique has been used to investigate many semiconductor heterostructures. Among them, GaN-based heterostructures including sapphire substrates were taken as examples. Using the X-ray CTR scattering together with the X-ray reflectivity measurements, the following results were obtained. (1) Amorphous-like layers were formed on the sapphire substrates when the substrates were heated at 1150°C in H2. (2) 50-100 Å thick amorphous-like AlN layers were formed on the sapphire substrates that were exposed to NH3for 10 min at 1150°C (nitridation process). (3) When the temperature was lower than 800°C, the amorphous-like AlN layers were not formed on the substrates even when exposed to NH3. Effects of nitridation process and AlN buffer layer (the low-temperature-deposited amorphous-like AlN layer) on the quality of GaN and GaInN overlayers were described. © 2002 Elsevier Science B.V. All rights reserved.
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