Divacancy-related complexes in Si(1−x)Ge(x)

In the present work, V2-related defects have been studied in SiGe alloys by means of infrared (IR) absorption spectroscopy, electron paramagnetic resonance (EPR) and deep-level transient spectroscopy (DLTS). The defects have been induced by electron irradiations at 80 K and subsequent isochronal anneals. In oxygen-lean SiGe samples after annealing out of Ge-V centers in the temperature range of 250-300 K an absorption band with maximum at about 5680 cm−1 has been found. An appearance of a new EPR signal Si-UA1 has been registered simultaneously. It is found from an analysis of the angular dependences of the EPR spectrum that the corresponding center has monoclinic-I symmetry with the principal values of g tensor: g1=2.0154, g2=2.0084 and g3=2.0039. It is argued that the absorption line and the EPR signal are related to Ge-V2 complex. The formation of Ge-V2 centers has also occurred upon heat treatments of SiGe samples in the temperature range of 400-450 K. It is associated with the capture of mobile divacancies by Ge atoms. The disappearance of the Ge-V2 center upon heat treatments at T>480 K is found to result in a shift of the absorption band to lower frequencies and in a shift of a DLTS peak associated with the Ge-V2(+/0) transition to higher temperatures. It is suggested that these shifts are related to a conversion of Ge-V2 centers into Ge2-V2 complexes.