The effect of irradiation temperature on post-irradiation strain levels in Ge/sub x/Si/sub 1-x//Si strained layer heterostructures

Abstract

Double crystal X-ray diffraction (DCXRD), transmission electron microscopy (TEM), and Rutherford backscattering spectroscopy and channelling (RBS-C) were used to study the effect of irradiation temperature and ion-energy on the perpendicular strain (/spl epsiv//sub /spl perp//) in Ge/sub x/Si/sub 1-x//Si strained layer heterostructures. Room temperature irradiation was shown to increase /spl epsiv//sub /spl perp//. This effect was adequately modelled by assuming that irradiation caused additional strain due to excess interstitial distribution. The effects of irradiating at 253/spl deg/C were more complex, resulting in: (a) an increase in /spl epsiv//sub /spl perp// when the radiation damage profile was confined to the alloy layer; or (b) a decrease in /spl epsiv//sub /spl perp// when the damage profile extended through the alloy/substrate interface. Strain relaxation at elevated temperature is believed to be effected by loop-like defects which nucleate at or near the alloy/substrate interface during high energy irradiation.