Mechanism of the current flow in Pd-(heavily doped p-AlxGa1−x N) ohmic contact

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Abstract
The physical mechanism of the current flow in Pd-(heavily doped p-AlxGa1−x N) ohmic contact is studied. Chloride-hydride epitaxy was used to grow the p-Al0.06Ga0.94N solid solution with uncompensated acceptor concentration N a –N d ranging from 31018 up to 1019 cm−3. Thermal vacuum deposition and subsequent thermal treatment were used to form an ohmic Pd contact. It is shown that, after the thermal treatment, the Pd-p-Al0.06Ga0.94N barrier contact with a potential barrier height of about 2.3 V becomes ohmic and the barrier height decreases to approximately 0.05 V. For uncompensated acceptor concentration N a –N d =31018 cm−3, thermionic emission is found to be the main mechanism of the current through the Pd-p-Al0.06Ga0.94N ohmic contact. An increase in N a –N d to approximately 1019 cm−3 in the solid solution leads to a transition from thermionic emission (at high temperatures) to tunneling (at low temperatures).