Competition between deep impurity and dopant behavior of Mg in GaN Schottky diodes

The effect of the deep acceptor Mg on the electrical characteristics of p-d oped GaN Schottky diodes is analyzed. The theoretical study is based on the numerical resolution of the basic semiconductor equations, including the c ontinuity equation for the Mg-related acceptor level. It gives the steady-s tate and small-signal analysis of p-doped GaN:Mg Schottky diodes, yielding as final result the frequency dependent capacitance and conductance of the structure. It is shown that the low-frequency characteristics are determine d by the carrier exchange between the Mg related impurity level and the val ence band, whereas above the impurity transition frequency, the hole modula tion of the depletion layer edge governs the electrical response. Detailed results are shown on the effect of temperature, applied steady-state voltag e and series resistance. The study of two back-to-back connected GaN Schott ky diodes reveals the appearance of typical features in the electrical char acteristics, depending on the respective Schottky barrier height of the two junctions. (C) 2001 American Institute of Physics.