INVESTIGATIONS OF ELECTRON-BEAM AND OPTICAL INDUCED DAMAGE IN HIGH-MOBILITY SIGE HETEROSTRUCTURES

Modulation-doped two dimensional electron gases (2DEGs) grown on Si0.7 Ge0.3 virtual substrates were investigated. Low temperature measuremen ts were used to characterise the uniformity of the wafers and annealin g studies demonstrated that high annealing temperatures (above 600 deg rees C) destroyed the electrical properties. Studies of excimer irradi ation of the 2DEG material demonstrated that only surface damage was i nduced, but the subsequent annealing of this damage reduced the carrie r density in the material, suggesting strain relaxation of the straine d Si cap. Electron beam irradiation experiments at 40 keV and PMMA dos es showed charging effects at room temperature but little damage. Fina lly a number of narrow channel devices were fabricated using 300 keV e lectrons and characterised at low temperature to estimate the range of the electron-beam induced damage. (C) 1997 Elsevier Science Ltd.