Characterization of m-GaN and a-GaN Crystallographic Planes after Being Chemically Etched in TMAH Solution

Nedal Al Taradeh,Luong-Viet Phung,Ali Soltani,Hassan Maher,Florian Tendille,Eric Frayssinet,Yvon Cordier,Frederic Morancho,Camille Sonneville,Christophe Rodriguez

doi:10.3390/en14144241

Abstract

This paper proposes a new technique to engineer the Fin channel in vertical GaN FinFET toward a straight and smooth channel sidewall. Consequently, the GaN wet etching in the TMAH solution is detailed; we found that the m-GaN plane has lower surface roughness than crystallographic planes with other orientations, including the a-GaN plane. The grooves and slope (Cuboids) at the channel base are also investigated. The agitation does not assist in Cuboid removal or crystallographic planes etching rate enhancement. Finally, the impact of UV light on m and a-GaN crystal plane etching rates in TMAH has been studied with and without UV light. Accordingly, it is found that the m-GaN plane etching rate is enhanced from 0.69 to 1.09 nm/min with UV light; in the case of a-GaN plane etching, UV light enhances the etching rate from 2.94 to 4.69 nm/min.

Highlights

As a wide-bandgap transistor technology, GaN provides a compelling opportunity to achieve unprecedented performance levels and efficiency in power electronics systems, owing to its large breakdown electric field and high Baliga’s Figure of merit [1,2,3,4]
It guarantees a 10% reduction of losses in power conversion circuits [5]. It offers faster, cooler and smaller power devices than its silicon counterparts [6,7]. Both lateral and vertical structures have been considered to be incorporated in the GaN power devices [8]
The purpose of this paper is to investigate one of the most critical steps in the fabrication process of vertical GaN FinFET transistors, which is the etching of the channel sidewalls

Summary

Introduction

As a wide-bandgap transistor technology, GaN provides a compelling opportunity to achieve unprecedented performance levels and efficiency in power electronics systems, owing to its large breakdown electric field and high Baliga’s Figure of merit [1,2,3,4] It guarantees a 10% reduction of losses in power conversion circuits [5]. Contrariwise, the vertical GaN power devices, especially the GaN FinFET, have garnered considerable attention because of their potential to reach high voltage and high output current density [12,13] They exhibit superior thermal performance compared to lateral devices [14]. The first design and fabrication of a Normally-Off GaN vertical fin power FET (or MOSVFET) have been reported by W

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Conclusion