Polarity Control of GaN and Realization of GaN Schottky Barrier Diode Based on Lateral Polarity Structure

Abstract

This paper reports investigation on a polarity control scheme of GaN thin films and realization of Schottky barrier diode (SBD) fabricated on a lateral-polarity-structure ('PS) GaN without intentionally doping. Specifically, Ga-polar and N-polar GaN were grown simultaneously side by side on sapphire substrate with patterned AlN buffer. Due to the surface energy difference between two polarities, N-polar regions are n-type conductive with rough surface morphology, while Ga-polar regions are semiinsulating with atomic flat surface morphology. Annealing conditions of both ohmic contact and Schottky contact were investigated. Current-voltage (I-V) characteristic revealed that the SBD fabricated on 'PS GaN has higher forward current, barrier height closer to 0.7 eV, and ideality factor closer to unity compared to SBD fabricated on conventional undoped GaN. The specific on-state resistance (RON) for the SBD based on 'PS GaN is 77 mQ · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> lower than the SBD fabricated on conventional GaN. With oxide passivation on SBD surface, forward current exceeds 0.2 A at 10 V, while reverse current is less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> A at -10 V, respectively. The utilization of 'PS in SBD demonstrates a promising approach for the development of lateral n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> SBD with a simple fabrication scheme.