X-Ray Diffraction Characterization of CdTe Epitaxial Layers on GaAs Substrates as a Function of Temperature

摘要

X-ray diffraction methods have been used to study the structural and thermal properties of CdTe epitaxial layers on GaAs substrates. Precession photography revealed twin faults in (1,1,1) oriented CdTe epilayers. Measurements of the Bragg reflections between 10 and 360 deg K reveal anomalous behavior in the lattice parameters of both the substrate and the epilayer in a (0,0,1) oriented sample deposited at 410 deg C. The overall change in the CdTe lattice parameter in this temperature range was about five times larger than in bulk CdTe, and the change in the substrate lattice parameter was about three times the bulk value. These anomalies were absent in a similar sample deposited at 380 deg C. Similar measurements were made on GaAs and CdTe single crystals. The Debye temperatures derived from perpendicular reflections are 250 deg K for the GaAs substrates and 142 deg K for the CdTe epilayers. These are the same as for single cyrstals of GaAs and CdTe. The Debye temperatures from reflections not perpendicular to the surface are significantly lower. The Debye theory and the One-Particle Potential model are used in the above analyses. The Debye-Einstein theory does not explain the observed behavior any better than the Debye theory. 140 refs., 53 figs. (ERA citation 12:009462)