Current-voltage characteristics of MBE-grown strained Si1-xGex/Si heterojunction diodes and their temperature dependence

Abstract

Studies of current-voltage (I-V) characteristics and their temperature dependence show that the current transport in MBE-grown Si1-xGex/Si diodes is closely related to the epitaxial film quality. It is mainly controlled by two different mechanisms at low and high temperature. The ideality factor n of the diodes increases as the temperature is reduced, and n increases faster for the diodes which have larger n at room temperature. From comparisons with calculated results, it is proposed that the transport mechanism is diffusion controlled at high temperature and defect-assisted tunneling controlled at low temperature. The results from ? irradiation studies also support this suggestion. Due to the existence of band-offsets, the shift of the I-V curve with temperature of p+-Si1-xGex/n-Si diodes is much smaller than that in n+-Si1-xGex/p-Si diodes, when the current is diffusion controlled. The band-offsets are estimated from these shifts, and the results are in agreement with values measured by another method.