Observation of defects evolution in strained SiGe layers during strain relaxation

a r t i c l e i n f o Misfit defects in strained-SiGe layers grown on (100) Si-substrates by reduced pressure chemical vapor deposition (RPCVD) were investigated by using high-resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM). While (004) omega rocking curve (ω-RC) is not sensitive to 60° misfit dislocations in a slightly strain-relaxed sample, they caused an asymmetrical shape to (113) ω-RC. On the other hand, it was found that the partial dislocations associated with stacking faults in highly strain-relaxed sample contributed to significant and symmetric peak broadening of both ω-RCs. Strained-SiGe layers play an important role in advanced devices due to their enhanced charge carriers mobility and band-gap engineering possibilities in optoelectronics [1–3]. During device fabrication processes that involve high temperature steps, strained layers could relax via defects generation, such as misfit or threading dislocations, degrading the device performance [4,5]. The stacking faults in strained layers generated during strain relaxation have been extensively studied. Kvam et al. reported general criteria for when stacking fault generation should be possible during strain relaxation as a function of substrate surface orientation [6]. Maree et al. found that the acting slip mechanism for the generation of misfit disloca-tions in mismatched semiconductor heterostructure showed that the dissociation of 60° dislocation into two partial dislocations was dependent of the strain types [7]. These extensive investigations to asses the relaxation of strained layers and observe the type and density of induced defects have been traditionally performed by using transmission electron microscopy (TEM). Unfortunately, despite the body of study on the defects evolution during strain relaxation, the investigation by using X-ray diffraction (XRD) techniques is deficient. Although the Ge interdiffusion at Si/SiGe interface during high temperature annealing was investigated by means of high-resolution X-ray diffraction by Zheng and Jang, the XRD study on the misfit dislocations remain relatively unclear [8,9]. We have investigated the effect of stacking faults as well as misfit dislocations on the broadening and shape of omega rocking curves (ω-RCs) of strained-SiGe layers with different Ge concentration and strain relief. Si 1 − x Ge x layers with a nominal Ge fraction x = 0.20 and 0.25 and a thickness of 50 and 100 nm were grown on (100) Si by reduced pressure chemical vapor deposition (RPCVD) at a pressure of 10 Torr and growth temperature of 700 °C using dicholorosilane (DCS, SiH 2 Cl 2) and germane (GeH 4) …