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

The physical mechanism of the current flow in Pd-(heavily doped p-AlxGa1-xN ) 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 3 x 10(18) up to 10(19) cm(-3). Thermal vacuum depositi on 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 barri er 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 ac ceptor concentration N-a - N-d = 3 x 10(18) cm(-3), thermionic emission is found to be the main mechanism of the current through the Pd-p-Al0.06Ga0.94 N ohmic contact. An increase in N-a - N-d to approximately 10(19) cm(-3) in the solid solution leads to a transition from thermionic emission (at high temperatures) to tunneling (at low temperatures). (C) 2001 MAIK "Nauka/Int erperiodica".