ELECTRICAL-PROPERTIES OF A-SIC/C-SI(P) HETEROJUNCTIONS

Electrical properties of heterojunctions consisting of amorphous silicon carbide (a-SiC) on p-type crystalline silicon (c-Si) have been investigated by measuring their current-voltage (I-V) and capacitance-voltage (C-V) characteristics, as well as the temperature dependence of their current (I). The I-V characteristics of a-SiC/c-Si(p) heterojunctions exhibit a low turn-on voltage and a high reverse breakdown voltage (about 140 V). It was found that a model of an abrupt anisotype crystalline heterojunction is valid for the a-SiC/c-Si(p) structure. This model, for values of forward-bias voltage lower than a critical value V(T), predicts that at fow temperatures (T < 250 K) recombination is the dominant transport mechanism, whereas at high temperatures (T > 250 K) recombination-diffusion becomes the dominant transport mechanism. For higher voltages (V > V(T)), the tunnelling process dominates in the whole temperature range studied. From I-V measurements of a-SiC/c-Si(p) heterojunctions it was concluded that the conductivity of undoped a-SiC is n-type. Finally, from C-V measurements, the value of electron affinity of a-SiC was obtained, for the first time, and it was found to be chi1 = 4.12 +/- 0.04 eV.