Current transport mechanisms and trap state investigations in (Ni/Au)–AlN/GaN Schottky barrier diodes

Abstract

The current transport mechanisms in (Ni/Au)–AlN/GaN Schottky barrier diodes (SBDs) were investigated by the use of current–voltage characteristics in the temperature range of 80–380 K. In order to determine the true current transport mechanisms for (Ni/Au)–AlN/GaN SBDs, by taking the J s(tunnel), E 0, and R s as adjustable fit parameters, the experimental J– V data were fitted to the analytical expressions given for the current transport mechanisms in a wide range of applied biases and at different temperatures. Fitting results show the weak temperature dependent behavior in the saturation current and the temperature independent behavior of the tunneling parameters in this temperature range. Therefore, it has been concluded that the mechanism of charge transport in (Ni/Au)–AlN/GaN SBDs, along the dislocations intersecting the space charge region, is performed by tunneling. In addition, in order to analyze the trapping effects in (Ni/Au)–AlN/GaN SBDs, the capacitance–voltage ( C– V) and conductance–voltage ( G/ω– V) characteristics were measured in the frequency range 0.7–50 kHz. A detailed analysis of the frequency-dependent capacitance and conductance data was performed, assuming the models in which traps are located at the heterojunction interface. The density ( D t ) and time constants ( τ t ) of the trap states have been determined as a function of energy separation from the conduction-band edge ( E c − E t ) as D t ≅ ( 5 – 8 ) × 10 12 eV - 1 cm - 2 and τ t ≅ ( 43 – 102 ) μ s , respectively.