Study of dislocations in strained-Si/Si0.8Ge0.2 heterostructures by EBIC, TEM and etching techniques

We have characterized threading dislocations (TDs) and misfit dislocations (MDs) in a degraded strained-Si/SiGe heterostructure by using electron beam induced current (EBIC), transmission electron microscopy (TEM) and chemical etching techniques. The strained-Si layer in this degraded heterostructure was selected to be thicker than the critical thickness for introducing MDs at the interface of strained-Si/SiGe. Cross-sectional TEM image reveals that there are dense dislocation network in deep region (graded SiGe layer) and 60° MDs at the upper interface (strained-Si/SiGe interface). The EBIC image taken with a 20 keV electron beam reveals the cross-hatch pattern of MD network in the deep graded SiGe region. The EBIC image taken with a 4 keV electron beam at 65 K shows weak dark spots and two perpendicular sets of weak dark lines, corresponded to TDs and MDs at the upper interface, respectively. Comparison with chemical etching results indicates that the weak dark lines in EBIC image correspond to MD bundles/groups at the upper interface. The electrical activities of these dislocations are discussed by using the temperature dependence of EBIC contrast