Effect of modifying a Bi nanolayer on the charge transport in Sb-n-Si-Bi-Ge33As12Se55-Sb heterostructures

Abstract

The current-voltage characteristics of the Sb-n-Si-Ge33As12Se55-Sb and Sb-n-Si-Bi-Ge33As12Se55-Sb heterostructures are studied. It is found that the presence of bismuth atoms in the transition region causes the current through the structure to increase. The width of the space-charge region and, correspondingly, the extent of penetration of the contact field into the p-type region are in the range from 0.2 to 0.5 µm. The introduction of a modifying bismuth layer also leads to radical changes in the current-voltage characteristic, which indicates that the mechanism of the charge-carrier transport in the structure is changed. The introduction of the Bi nanolayer leads to the transformation of an abrupt heterojunction into a gradient heterojunction. A soft breakdown is not observed in the structures with the modified transition layer. The soft breakdown is observed at a reverse bias; the cutoff voltage of ∼0.62 V corresponds to the barrier height of 0.65 eV for electrons.