ANALYSIS OF ABNORMAL X-RAY-DIFFRACTION PEAK BROADENING FROM INGAAS GAAS MULTIPLE-QUANTUM WELLS/

Strain relaxation behavior in In0.2Ga0.8As/GaAs multiple quantum well (MQW) structures with various barrier thicknesses but with fixed well thickness was characterized by analyzing the x-ray rocking curves and low temperature photoluminescence. For the thick-barrier samples which have good optical characteristics, it is observed that the superlatti ce x-ray peaks are broadened nonuniformly. This anomalous behavior can be successfully simulated by considering the paired dislocation chara cter in the double-kink type strain relaxation. Meanwhile, the thin-ba rrier ones show deteriorated optical properties which can be attribute d to dislocations located at the MQW-substrate interface. This observa tion shows that two different relaxation mechanisms are working for th e thick-and thin-barrier cases, respectively. (C) 1997 American Instit ute of Physics.