Analysis of electrical properties and deep level defects in undoped GaN Schottky barrier diode

Electrical and deep level defects have been investigated in GaN Schottky barrier diode (SBD) in the temperature ranging from 125 K to 425 K. The study was carried out by combined current density-voltage (J-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) characterization techniques. It is found that the ideality factor n of the diode decreases and the corresponding Schottky barrier height (SBH) increases with increasing temperature, which indicates the barrier in-homogeneity at metal/semiconductor interface. Thermionic emission with Gaussian distribution of SBHs is thought to be responsible for the electrical behavior of the diode over the temperature region. The possible explanation for this discrepancy in the estimated SBHs from J-V and C-V is presented. The DLTS measurement has revealed two deep level traps in GaN with activation energies E_c - 0.23 eV and E_c - 0.45 eV having different capture cross-sections. In addition, we observed that the reverse leakage current in GaN SBD above 275 K is due to Frenkel-Poole emission (FPE). The estimated emission barrier height by FPE model is about ∼0.25 eV. Hence, the reverse leakage current is due to the emission of electrons from the trap state near the metal-semiconductor interface into a continuum of states, associated with conductive dislocations.