Forward current transport and noise behavior of GaN Schottky diodes

In this work, we first measure the forward temperature-dependent current-voltage (T-I-V) characteristics of the GaN-based Schottky diodes grown on the bulk GaN substrates, and then study the transport mechanisms of the forward current and the low-frequency current noise behaviors under various injection levels. The results are obtained below. 1) In a forward high-bias region the thermionic emission current dominates, and the extracted barrier height is about 1.25 eV at T = 300 K, which is close to the value measured by capacitance-voltage sweeping. 2) In a forward low-bias region (V < 0.8 V) the current is governed by the trap assist tunneling process, having an ideality factor much larger than 1, and the derived barrier height is about 0.92 eV at T = 300 K, which indicates that the conductive dislocation should be mainly responsible for the excessive leakage current, having a reduced barrier around the core of dislocations. 3) The Lorentzian noise appears only at very small current (I < 1 mu A) and low frequency (f < 10 Hz), whose typical time constant is extracted to be about 30 ms, depending on the multiple capture and release process of electrons via defects. 4) At a higher frequency and current, the low-frequency 1/f noise becomes important and the corresponding coefficient is determined to be about 1.1, where the transport is affected by the random fluctuation of the Schottky barrier height.

Automated summary

In this study, the T-I-V characteristics of GaN-based Schottky diodes were measured to investigate the transport mechanisms and low-frequency current noise behaviors under various injection levels. The results show that different current mechanisms dominate in different bias regions, with conductive dislocations being mainly responsible for excessive leakage current. The analysis reveals the impact of Schottky barrier height fluctuations on transport at higher frequencies and currents.