Investigation on Carrier Transport Through AlN Nucleation Layer From Differently Doped Si(111) Substrates

To get a better insight into the vertical leakage mechanism of GaN-on-Si, the carrier transport from n
⁺
, n, p
⁺
, and p-Si(111) substrates through the AlN nucleation layer was investigated. A plateau in the current-voltage curve was found only for the AlN/p-Si heterojunction due to depletion of the p-Si substrate. Detailed study illustrated that it was the leaky AlN that cannot effectively block the increasing amount of electrons in the inversion layer at the interface and triggered the depletion. Temperature-dependent characterization suggested that the forward vertical leakage mechanism of AlN/Si could be explained sequentially by Ohm's law, space-charge-limited conduction, variable-range hopping, and trap-assisted tunneling. A model involving shallow donor traps, interface traps, and deep level traps was proposed to explain the leakage characteristics. This paper shows that the carrier concentration of the Si substrates strongly impacts the vertical leakage characteristics, and also that the carrier transport from the Si substrate through the AlN nucleation layer is heavily influenced by traps.