# 4.11 A/1650 V Sapphire-Substrate GaN MIS-HEMTs with Thin Buffer for Medium-Voltage Power Applications

## TL;DR

This paper introduces a cost-effective GaN power device using a sapphire substrate and thin buffer layer, achieving high voltage and current performance suitable for medium-voltage applications.

## Contribution

A CMOS-compatible process for sapphire-based GaN MIS-HEMTs with thin buffer layers is demonstrated, enabling high breakdown voltage and reliability.

## Key findings

- Devices achieved >1650 V breakdown voltage and >4.1 A on-state current with tight statistical distributions.
- Dynamic RON and leakage current remained stable under electrical stress at room temperature and 150 °C.
- Long-term reliability at 650 V was confirmed through high-temperature reverse bias aging tests.

## Abstract

The substantially lower breakdown electric field of Si compared to GaN necessitates thick buffer layers in Si-based GaN power devices for medium-voltage applications, significantly increasing cost. Recently, sapphire substrates, offering high electrical insulation and excellent mechanical strength, have emerged as a promising alternative. In this work, we demonstrate a CMOS-compatible process for sapphire-based GaN MIS-HEMTs utilizing a thin buffer layer. The fabricated devices with a WG of 20.4 mm and an LGD of 24 μm achieve a high off-state breakdown voltage >1650 V and a maximum on-state current > 4.1 A, with tight statistical distributions of VTH and RON across the wafer. Furthermore, statistical characterization results of dynamic RON and leakage current under electrical stress conditions at both room temperature and 150 °C, confirm operational viability at high temperatures. Finally, long-term reliability for 650 V operation is validated by high-temperature reverse bias (HTRB) accelerated aging tests.