OPTICAL INVESTIGATION OF STRAIN AND DEFECTS IN (100)CDTE GE/SI AND (100)ZNTE/GE/SI GROWN BY MOLECULAR-BEAM-EPITAXY/

Low temperature (1.7 K) reflectance and photoluminescence (PL) have be en used to assess residual strain and impurities in molecular beam epi taxial (100) CdTe/Ge/Si and (100) ZnTe/Ge/Si. Both types of samples ex hibit residual biaxial tensile thermal strain as expected from differe nces in previous thermal expansion data, but the measured magnitudes ( 0.72x10(-3) for CdTe/Ge/Si and 1.5x10(-3) for ZnTe/Ge/Si) are smaller than predicted. The results are consistent with either residual lattic e mismatch stress or partial relaxation of the thermal strain during c ooling. Residual accepters in the CdTe include Cu and a frequently obs erved 49 meV level, whose PL peaks lack the previously reported linear polarization. However, a new series of linearly polarized bound excit on lines is reported in CdTe. (C) 1997 American Institute of Physics.