Analysis of Leakage Mechanisms in AlN Nucleation Layers on p-Si and p-SOI Substrates

In this paper, the carrier transport mechanisms in AlN nucleation layers grown by MOCVD on p-Si and p-silicon-on-insulator (SOI) substrates were investigated by using electrical characterizations at various electric fields and temperatures on Ni-Au/AlN/Si metal-insulator-semiconductor capacitors. For the case of the AlN on Si substrate, different contact schemes, i.e., top-bottom versus top-top, have been compared. It was found by capacitance-voltage measurements that an inversion channel related to the Shockley-Read-Hall (SRH) minority carrier generation in the silicon bulk and SOI substrates was formed. It showed that the AlN on p-SOI platform exhibited the same leakage mechanisms as for the AlN on the Si substrate. The contact scheme mainly affects the low forward and reverse bias characteristics, by adding a surface leakage contribution. At increasing the forward (positive) gate bias, the carrier transport process becomes in turn ohmic, variable-range hopping, SRH generation, and Fowler-Nordheim (FN) direct tunneling. Moreover, at the reverse bias, the carrier transportation is in turn dominated by the Schottky emission, Poole-Frenkel (PF) conduction, and FN direct tunneling with increasing bias.