Experimental evidence demonstrated an increase in the relaxation which accompanied hole emission from vacancies in non-strained p-type alloys, as compared with pure Si. Such a vacancy was known to destroy the rigidity of the lattice. This, in turn, strongly affected the vibrational modes and made large lattice relaxations possible. As the Ge content was increased, deep-level transient spectroscopic measurements revealed a constant hole ionization enthalpy; with a marked increase in the emission-rate pre-factor. The analysis showed that this increase could be accounted for by an entropy term which was caused by a lattice relaxation specific to the statistical alloy coupling disorder and which was responsible for a large carrier-phonon around the vacancy.

Vacancy in Relaxed p-Type Si1-xGex Alloys - Evidence for Strong Disorder-Induced Relaxation A.Mesli, A.Nylandsted Larsen: Physical Review Letters, 1999, 83[1], 148-51