Electronic States In Glow-Discharge a-SiGex:H:(F) Alloys

Amorphous SiGex films with low spin densities and high photoconductivity were prepared by the glow discharge of a gaseous mixture of SiF4-GeF4-H2. The transport properties of a-SiGex:H:(F) were investigated by the time-of-flight method. The electron transport was found to be non-dispersive at room temperature with a drift mobility of 0.2-0.3 cm2/ Vs, while the transient hole current consisted of a fast non-dispersive process and slow emission from deep states. The non-dispersive hole transport may be due to narrow tail states of the valence band. The nature of the deep defect states in a-SiGex:H:(F) is disscussed in terms of a defect type consisting of twofold-coordinated Ge.