Optimization of recess-free AlGaN/GaN Schottky barrier diode by TiN anode and current transport mechanism analysis

Abstract

In this work, the optimization of reverse leakage current (I R) and turn-on voltage (V T) in recess-free AlGaN/GaN Schottky barrier diodes (SBDs) was achieved by substituting the Ni/Au anode with TiN anode. To explain this phenomenon, the current transport mechanism was investigated by temperature-dependent current–voltage (I–V) characteristics. For forward bias, the current is dominated by the thermionic emission (TE) mechanisms for both devices. Besides, the presence of inhomogeneity of the Schottky barrier height (qφ b) is proved by the linear relationship between qφ b and ideality factor. For reverse bias, the current is dominated by two different mechanisms at high temperature and low temperature, respectively. At high temperatures, the Poole–Frenkel emission (PFE) induced by nitrogen-vacancy (V N) is responsible for the high I R in Ni/Au anode. For TiN anode, the I R is dominated by the PFE from threading dislocation (TD), which can be attributed to the decrease of V N due to the suppression of N diffusion at the interface of Schottky contact. At low temperatures, the I R of both diodes is dominated by Fowler–Nordheim (FN) tunneling. However, the V N donor enhances the electric field in the barrier layer, thus causing a higher I R in Ni/Au anode than TiN anode, as confirmed by the modified FN model.