Ge composition dependence of the minority carrier lifetime in monocrystalline alloys of Si 1−xGe x

Abstract

In this work we have investigated the influence of the Ge composition on the minority carrier lifetime in Czochralski (Cz) grown monocrystalline Si 1− x Ge x alloys in the composition range of 0< x<0.07. The lifetime measurements were performed by both microwave photo conductance decay ( μ-PCD) measurements and the quasi-steady-state photoconductance (QssPC) technique. Low-temperature (450 °C) anneals as well as phosphorous diffusion gettering were applied in order to investigate the possibility of improving the minority carrier lifetime in this material. A surface passivation method based on deposition of a double layer stack consisting of a hydrogenated amorphous silicon thin film capped by a silicon nitride anti-reflection coating was used. It is established that the minority carrier lifetime in the investigated alloys decreases dramatically with increasing Ge concentration. It is further shown that phosphorous gettering is the most effective method for the enhancement of bulk lifetime values in the Si 1− x Ge x alloys studied.