Novel high drain breakdown voltage AlGaN/GaN HFETs using selective thermal oxidation process

Abstract

We have developed novel selective thermal oxidation process for AlGaN/GaN Heterostructure Field Effect Transistors (HFETs) and realized extremely high device isolation and high drain breakdown voltage device of over 1OOV The leakage current of device isolation between two active islands exhibited drastic reduction of 5 order of magnitude smaller than that of conventional mesa isolation process. Moreover, the fabricated 1.3um-gatelength AlGaN/GaN HFETs exhibited maximum transconductance ( g m d of 130mS/mm, maximum drain current (I,-) of SOOmA/mm and excellent pinch off characteristics at high drain voltage of over 120V.heterostructure is that the density of 2DEG is extremely high, more than 1 X lOI3 by the piezoelectric effect and spontaneous polarization effects(3). One-order magnitude higher output power can be expected by simply changing the material.

Reduction in Gate Leakage Current of AlGaN/GaN HEMT by Rapid Thermal Oxidation

“…Also, it has been suggested that deposition of a thin layer of Al to prior to oxidation improves the uniformity of oxidation. However, the oxidation rate reported there is much higher compared to that of the other reports [6][7][8][9]. No such degradation was obvious from the gate I -V and C -V characteristics obtained in our case.…”

“…Thermal oxidation of the barrier AlGaN has also been considered for gate dielectric and device isolation [6][7][8][9]. Large reduction in the leakage current has been reported for selective thermal oxidation isolation over mesa isolation [6]. MOS HEMTs with thermally grown oxide at 900 °C have been reported by Inoue et al [8].…”

Low-Temperature and Rapid Oxidation of GaN Surface by Saturated Water Vapor at High Pressure

“…It is reported that conventional dry oxidation at 900 C for 60 min forms an approximately 60 nm thick Ga oxide layer on a GaN surface. 10) The oxidation rate obtained by the saturated water vapor treatment at 350 C is higher than the conventional dry oxidation rate at 900 C. This rapid oxidation potential at low temperatures is attributed to the high density of the oxidizer (H 2 O) under the high-pressure condition. As indicated in Table I, the H 2 O density of saturated water vapor is 113.6 kg/m 3 .…”

Enhanced Device Performance of AlGaN/GaN High Electron Mobility Transistors with Thermal Oxidation Treatment

“…12) Besides, by preannealing of AlGaN under the oxidation ambient, the improvement of Schottky barrier height on the AlGaN/GaN heterostructure has been observed by Jeon et al 4) In addition, thermal oxidation process could be a favorable way to achieve the electrical insulation of the AlGaN/GaN heterostructure devices. A selective deep thermal oxidation was proposed by Masato et al 13) to obtain interdevice insulation in the AlGaN/GaN HEMTs, instead of the conventional insulation process, such as dry etching or ion implantation.…”