Deep acceptor complex in thermally processed Ge-Si〈Ga,Ni〉 crystals

Abstract

Based on experimental data on the temperature dependences of the free carrier concentration in complex-doped Ge1 − xSix 〈Ga,Ni〉 crystals (0 ≤ x ≤ 0.25), it is established that sample quenching at 1020–1050 K leads to the formation of additional acceptor centers in them. The activation energy of these centers increases with an increase in silicon content in the matrix and is described by ratio Ekx = Ev + (75 + 420x) meV. Crystal annealing at 550–570 K leads to the disappearance of additional acceptor levels. An analysis of the data shows that the most likely model for these deep acceptors is a complex composed of substituent nickel and gallium atoms (NisGas) or an interstitial nickel atom and a substituent gallium atom (NiiGas). It is established that the generation of additional electroactive centers in Ge1 − xSix 〈Ga,Ni〉 must be taken into account in precisely controlling the electronic properties of crystal via the decomposition of supersaturated solution of nickel impurity in the matrix.