Normally-off AlGaN/GaN HFETs using NiO<inf>x</inf> gate with recess

Abstract

The normally-off AlGaN/GaN HFETs on Si substrate were fabricated. To realize normally-off characteristic, recess was formed under the gate electrode and NiOx was formed as a gate electrode. As a result, the fabricated AlGaN/GaN HFET with a gate width of 157 mm exhibited a threshold voltage of +0.8 V, a breakdown voltage of more than 800 V, an onresistance of 72 mΩ, and a maximum drain current of more than 20 A. The on-resistance-area product (Ron×A) was 0.28 Ω･ mm 2 . This value is approximately 1/28 compared with that of conventional Si MOSFETs. The gate leakage current was decreased about four orders of magnitude smaller than the conventional normally-on HFETs. The NiOx gate electrode operates as a p-type material.

Technology and Reliability of Normally-Off GaN HEMTs with p-Type Gate

“…The principal idea has also been taken up by other institutions leading to very successful GaN normally-off devices [24,25]. In a concept variation, the extrinsic p-type semiconductor material NiO x has been taken instead of a III-N semiconductor [26]. P-type Gates for GaN HFETs can also get combined with an AlGaN-barrier gate recess to further enhance the threshold voltage without sacrificing the 2DEG electron concentration in the access region [26].…”

“…In a concept variation, the extrinsic p-type semiconductor material NiO x has been taken instead of a III-N semiconductor [26]. P-type Gates for GaN HFETs can also get combined with an AlGaN-barrier gate recess to further enhance the threshold voltage without sacrificing the 2DEG electron concentration in the access region [26]. State-of-the-art p-GaN gate transistors with 600 V breakdown strength feature one-volt threshold voltage, low off-state leakage currents of 10 nA/mm for zero-volt gate bias and 0.4 A/mm drain current for on-state conditions at typically five-volt gate bias (Figure 4a Figure 3a sketches the basic structure of a p-GaN gated device.…”

High-Voltage AlGaN/GaN High-Electron-Mobility Transistors Using Thermal Oxidation for NiOxPassivation

“…NiO x has been studied as a p-type ohmic contact in GaN light-emitting diodes [12]. It has also been reported that NiO x can be used in the gate of normally-off AlGaN/GaN high-electron-mobility transistors (HEMTs) [13] and MOS-HEMTs [14]. The authors successfully suppressed the leakage current of GaN Schottky barrier diodes via oxidation during the fabrication process [11].…”

A 95% Efficient Normally-Off GaN-on-Si HEMT Hybrid-IC Boost-Converter with 425-W Output Power at 1 MHz

“…New large potential markets for GaN which include motor inverters, solar DC/DC converters, and grid inverters, require operation at about 350V and switches rated for 600V. Several groups are developing high voltage GaN HEMTs and have achieved breakdown voltage of 1800 V [3], scaled current of 120 A [4] and achieved 98% efficiency at 1 MHz switching [5]. Safe operation requires normally-off switches for many high voltage applications, such as automobile and grid-tied inverters.…”