Vacancy-related deep levels in n-type Si1-xGex strained layers - art. no. 245322

Deep-level transient spectroscopy (DLTS) studies of 2-MeV proton-induced de fect electronic levels in strained epitaxial Si1-xGex, 0 less than or equal tox less than or equal to0.13, layers have been performed. It is found tha t the irradiation results in the formation of a dominant peak in the DLTS s pectra for all compositions. Isochronal 20-min annealing studies of the obs erved deep level have revealed that the peak anneals out at 100-200 degrees C. This peak is identified as the vacancy-phosphorous (VP) pair. The compos itional dependence of the activation enthalpy of the VP pair is nonlinear, with a sharp increase for x = 0.04 and little variation for higher Ge conce ntrations. After annealing of the VP pair, the dominating defect level is a ssigned to the single acceptor state of the divacancy [V-2(-/0)]. The doubl e-acceptor state [V-2(=/-)] is observed to be strongly suppressed in the st rained Si1-xGex layers. The compositional dependence of the activation enth alpy of V-2(-/0) is relatively weak, with a small decrease in the activatio n enthalpy. It is found that formation of V-2 in the strained Si1-xGex laye rs is enhanced with respect to that in Si. This is associated with an incre ased concentration of vacancies in the strained layer, acting as a sink for vacancies migrating in the substrate.