Deeply and vertically etched butte structure of vertical GaN p–n diode with avalanche capability

Abstract

A vertical p–n diode with a simple edge termination structure on a GaN free-standing substrate is demonstrated. The edge of this device is terminated simply by etching a drift layer deeply and vertically. A device simulation revealed that the electric field at the device edge was more relaxed and uniformly applied by etching the mesa deeper than the depletion region. The fabricated device showed low leakage current and avalanche capability, and its breakdown characteristics could be reproduced many times. By emission microscopy observation, we found that there was no leakage current at the side wall of the device and that avalanche breakdown occurred throughout the inside of the device. This indicates that the electric field crowding at the side wall of the device was completely suppressed and a uniform electric field distribution was obtained by this structure.

Challenges and Perspectives for Vertical GaN-on-Si Trench MOS Reliability: From Leakage Current Analysis to Gate Stack Optimization

“…Fully vertical GaN-on-GaN diode and transistor demonstrators have reported excellent performances (up to 3-4 kV capability [16][17][18][19][20][21][22][23][24]). However, GaN substrates are small and expensive, with wafer costs per unit area for GaN-on-GaN ranging up to $ 100/cm 2 for 2-inch wafers [25,26].…”

On the Scope of GaN-Based Avalanche Photodiodes for Various Ultraviolet-Based Applications

“…An edge termination that can provide extra negative charges to terminate the electric field lines at the device boundary to reduce any localized peak electric field at any surface or corners is important for the realization of an APD. Figure 3 shows several edge terminations that were proposed for avalanche GaN p-n diodes, including the ion implantation-based edge termination (Kizilyalli et al, 2013;Ji et al, 2020a), etch-based edge termination (Fukushima et al, 2019;Maeda et al, 2018), and field-plated edge termination in which the field plate is connected to the anode electrode (Nomoto et al, 2016;Ohta et al, 2019). The schematic of the electric field distribution in the GaN p-n diodes with and without the ion-implanted edge termination is shown in Figure 4.…”

“…Figure 4B shows the schematic of a GaN p-n diode with the ion-implanted moat etch termination (Ji et al, 2020a), where the corners are rounded during isolation and can effectively reduce the localized peak electric field. (Fukushima et al, 2019); (D) field plate edge termination (Nomoto et al, 2016;Ohta et al, 2019); and (E) moat etch edge termination with ion implantation compensation (Ji et al, 2020a). compensate for the dry etching-induced damages, eliminating the leakage current through the etched surface.…”

“…On bulk GaN substrates, lo and behold, the impact ionization and avalanche breakdown were finally reported in p-i-n diodes in 2013 by Avogy Inc. (Disney et al, 2013). Since then, multiple research groups have reported the avalanche breakdown in GaN p-n diodes and extended the capability to Junction Field-Effect Transistors (JFETs) (Kizilyalli et al, 2013;Nomoto et al, 2016;Cao et al, 2018;Maeda et al, 2018;Ji D. et al, 2019;Maeda et al, 2019a;Fukushima et al, 2019;Ohta et al, 2019;Ji et al, 2020a;Ji et al, 2020b;Ji and Chowdhury, 2020;Liu et al, 2020;Liu et al, 2021). Our GaN APDs (Ji et al, 2020b), were also grown on the bulk GaN, which fulfilled the first requirement of high-qualitylow defect density (LDD) epitaxial films.…”

Estimation of Shockley–Read–Hall Lifetime in Homoepitaxial n‐GaN on Low‐Dislocation‐Density GaN Substrates Prepared by Hydride Vapor Phase Epitaxy and Maskless 3D

“…[1][2][3][4] Among GaN power devices, vertical devices have attracted much attention from the viewpoints of power-conversion and chip-size efficiencies. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The development of high-quality GaN substrates has made it possible to easily fabricate vertical p þ n diodes on freestanding substrates. A record high breakdown voltage of 5 kV has been achieved in combination with a low on-resistance R on of 1.25 mΩ cm 2 at a forward voltage V F of 5 V. [14] The quality of substrates has also been improved.…”