Electrical characterization of n-type a-SiGe:H/p-type crystalline-silicon heterojunctions

Abstract

Heterojunctions with an n-type hydrogenated amorphous silicon germanium (a-SiGe:H) on p-type crystalline-silicon heterojunctions were fabricated and electrically characterized. The electrical characterization was made by current density–voltage (J–V) and capacitance–voltage (C–V) measurements. The C–V results confirm the existence of an abrupt heterojunction. The temperature dependence of the J–V curves shows that in the forward conduction at low bias voltage (V < 0.45 V) the current density is determined by the recombination on the n-type a-SiGe:H depletion region, while at higher voltages (V > 0.5 V), the space charge limited effect becomes the main transport mechanism. The conduction and valence band discontinuities of the heterojunction and the electron affinity of the n-type a-SiGe:H film were calculated using Anderson's model. Under reverse bias conditions the J–V curves suggest that the current density is limited by hopping through the localized states into the gap. One-dimensional (1D) simulations support the proposed transport mechanisms.