2.5 kV/1.95 GW/cm² AlGaN/GaN-Based Lateral Schottky Barrier Diodes With a High-k Field Plate to Reduce Reverse Current

In this article, we present AlGaN/GaN-based lateral Schottky barrier diodes (SBDs) on sapphire substrate with fully recessed anodes and $\text{a}\vphantom {_{\int }}$ high-permittivity field plate (FP). A specific ON-resistance of 3.2 $\text{m}\Omega \cdot $ cm2, an on/off current ratio of $10^{{10}}$ , and a reverse breakdown voltage (BV) of 2.5 kV are simultaneously achieved for the device with the anode-to-cathode space of 30 $\mu \text{m}$ . This yields a Baliga’s power figure-of-merit (BFOM) of 1.95 GW/cm2. Our fabricated device shows that the leakage current is hardly affected by the reverse bias. It is because the electric field is pushed apart from the Schottky contact region by the high-permittivity FP. This causes the absence of the defect-related carrier tunneling effect at the Schottky contact region. Meanwhile, the high-permittivity FP helps extend the depletion effect for the drift region and gives rise to the increased BV.

I. Introduction

GaN-based power devices have attracted great attention for next-generation high-power applications due to their unique material properties, such as high critical electric field of 3.8 MV/cm, wide bandgap of 3.44 eV, large electron saturation velocity, and excellent thermal conductivity [1]. However, one of the great challenges is to obtain high breakdown voltage (BV) while having low specific ON-resistance (), which helps to reduce the conduction and switching losses for high-power-switching systems [2], [3]. Lateral GaN-based power devices such as AlGaN/GaN Schottky barrier diodes (SBDs) and high-electron-mobility transistors (HEMTs), can effectively reduce the resistance due to the high density and the high mobility of 2-D electron gas (2DEG) at AlGaN/GaN interface [4]. Recently, a great deal of effort has been made to improve device performance. The BV can be increased by homogenizing the electric field so that the drift region can be more effectively depleted. Hence, different junction termination technologies have to be utilized, such as the gated-edge termination [5], [6], field plates (FPs) [7], [8], [9], [10], floating field rings [11], [12], and p-GaN termination [13], [14], [15]. FP edge termination has been widely used in lateral AlGaN/GaN SBDs among other candidates because of the mature process and the effective charge-coupling effect. A recessed anode also proves to be useful in reducing the ON-resistance because the metal is directly contacted with the 2DEG [16], which is more easily fabricated. However, the dry-etching-caused surface defects may cause strong defect-related tunneling at the Schottky contact interface [17], which may cause the early breakdown for devices. Hence, methods to suppress the impact of surface defects have to be found, such as KOH wet etching [18], thermal annealing process [14], tetramethylammonium hydroxide (TMAH) treatment [19], a combination of hydrochloric acid treatment, and annealing process [20].