Electronic transport mechanism for nonalloyed Ti-based Ohmic contacts to n-AlGaN

We have investigated the carrier transport mechanism of nonalloyed Ti-based Ohmic contacts to n-AlGaN using current-voltage-temperature and the specific contact resistance-temperature relations. It is shown that the theoretical result obtained using the field emission mode through the shallow-donor-assisted tunneling model is in agreement with the experimental data, although there is a small deviation below 383K. The deviation is attributed to an increase of the self-compensation between donor-type and acceptorlike defects. This indicates that the electronic transport of the AlGaN contacts is sensitively dependent on Ga and oxygen/nitrogen related surface point defects.

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