Demonstration of Al0.85Ga0.15N Schottky barrier diode with > 3 kV breakdown voltage and the reverse leakage currents formation mechanism analysis

Abstract

In this paper, high performance lateral Al0.85Ga0.15N Schottky barrier diodes (SBDs) with a field-plate structure and a heavily doped GaN cap layer in the Ohmic region are demonstrated. Employing Al0.85Ga0.15N rather than AlN for the channel layer effectively reconciles the tension between electron mobility and dopant activation caused by AlN material dilemma. The lateral Al0.85Ga0.15N SBD with an anode-cathode spacing (LAC) of 20 μm achieves a specific on-resistance (Ron,sp) of 0.19 Ω·cm2 and a breakdown voltage exceeding 3 kV, rendering Baliga's power figure of merit of more than 47 MW/cm2, which is the highest value among all AlN- or Al-rich-AlGaN (Al ratio > 70%)-based diodes. Reverse leakage current mechanisms of Al0.85Ga0.15N SBDs are dominated by a variable range of hopping and trap-assisted space charge-limited conduction before destructive breakdown occurs in the field-plate oxide, which are verified by analyzing the reverse leakage characteristics. Combined with the stable performance with temperature up to 275 °C, the Al0.85Ga0.15N SBD shows great promise for next--generation high power electronics applications after further resolving the Ohmic and electron mobility issues.