Transport Measurements in LPCVD Amorphous Silicon Obtained from Disilane.

Abstract

ABSTRACTMeasurements of high temperature conductivity on a-Si:H obtained by LPCVD from Si2H6 at temperatures between 450 and 500 °C indicate clearly a change on the activation energy from 0.9 - 1.0 eV to 0.55 - 0.6 eV around 600 °K.The results are not strongly different from those obtained in GD a- SiH4:however, the coefficent of the energy shift of the mobility edge with temperature is greater by a factor of 2, while the average extension of the tail state distribution at T= 0 °K is roughly a factor 1.5 larger. The main discrepancy concerns the pre-exponential factor, which is one or two orders of magnitude larger, giving a product (NcukT)of the order of 1021 cm-1 s-1. By assuming a conduction mobility two orders of magnitude larger than the maesured Hall mobility one obtains a value for N which is only a factor four times larger than what currently assumed for a-Si:H.