Relaxation Defect Characterization of RTCVD Si1-xGex/Si Heterostructjres by Electrical and Optical Techniques

Abstract

ABSTRACTPhotoluminescence (PL) and deep level transient spectroscopy (DLTS) measurements have been carried out on Si1-xGex/Si heterostructures and Si/Si1-xGex/Si double heterostructures with fully strained or partially relaxed layers (0%<xGe<20%) grown by chemical vapor deposition using rapid thermal processing (RTCVD). This study reports strong PL and DLTS results connected to the establishment of relaxation defects in the SiGe layer and at the heterointerface which appear when the layer starts to relax. Strong broad PL bands (defect related) and sharp lines (similar to dislocation related D-lines on Si) have been detected and connected to this relaxation process. These PL results are strengthened by the clear observation, using DLTS experiments on relaxed layers, of interface traps with a maximum energy around Ev + 0.5eV resulting from the presence of misfit dislocations at the SiGe/Si hetero-interface and a deep level at Ev + 0.38eV related to dislocations or relaxation defects in the SiGe layer. Moreover, low temperature PL excitonic transition reported on Si/Si1-xGex/Si double heterostructures is described as a good tool to investigate the relaxation process which occurs in these heteroepitaxial layers.