Antireflective GaN Nanoridge Texturing by Metal-Assisted Chemical Etching via a Thermally Dewetted Pt Catalyst Network for Highly Responsive Ultraviolet Photodiodes

Abstract

Antireflective (AR) surface texturing is a feasible way to boost the light absorption of photosensitive materials and devices. As a plasma-free etching method, metal-assisted chemical etching (MacEtch) has been employed for fabricating GaN AR surface texturing. However, the poor etching efficiency of typical MacEtch hinders the demonstration of highly responsive photodetectors on an undoped GaN wafer. In addition, GaN MacEtch requires metal mask patterning by lithography, which leads to a huge processing complexity when the dimension of GaN AR nanostructure scales down to the submicron range. In this work, we have developed a facile texturing method of forming a GaN nanoridge surface on an undoped GaN thin film by a lithography-free submicron mask-patterning process via thermal dewetting of platinum. The nanoridge surface texturing effectively reduces the surface reflection in the ultraviolet (UV) regime, which can be translated to a 6-fold enhancement in responsivity (i.e., 115 A/W) of the photodiode at 365 nm. The results demonstrated in this work show that MacEtch can offer a viable route for enhanced UV light-matter interaction and surface engineering in GaN UV optoelectronic devices.

Enhanced Performance of Ultraviolet AlGaN/GaN Photo‐HEMTs by Optimized Channel Isolation Schemes

“…The biasing condition was set to be V gs = −10 V and V ds = 1 V unless otherwise specified. Performance parameters were extracted using the following equations, [ 39–41 ] $$$$\begin{equation} R = \frac{{{I}_{{\mathrm{photo}}} - {I}_{{\mathrm{dark}}}}}{{{P}_\lambda .S}}\end{equation}$$$$ $$$$\begin{equation} {\mathrm{PDCR}} = \frac{{{I}_{{\mathrm{photo}}} - {I}_{{\mathrm{dark}}}}}{{{I}_{{\mathrm{dark}}}}}\end{equation}$$$$ $$$$\begin{equation} {D}^* = \frac{{\sqrt S R}}{{\sqrt {2q{I}_{{\mathrm{dark}}}}}}\end{equation}$$$$where I photo and I dark are the photocurrent and dark current, P λ is the incident optical power density, S is the effective illuminated area and q is the elementary charge.…”

“…The biasing condition was set to be V gs = −10 V and V ds = 1 V unless otherwise specified. Performance parameters were extracted using the following equations, [39][40][41]…”

Metal-assisted chemical etching beyond Si: applications to III–V compounds and wide-bandgap semiconductors

“…Liao et al 111 investigated MacEtch of UID GaN as an alternative to wet chemical etching to fabricate nanoridge structures with favorable antireflective properties. An evaporated Pt nanomesh was deposited via electron-beam evaporation and the samples exhibited selectivity for vertical over lateral etching.…”

Gallium-V antireflective nanostructures by metal-assisted chemical etching for photodetector application

“…To quantitively evaluate the sensitivity of PDs to optical irradiation, responsivity (R) is one of the most important figures of merit. Responsivity is defined as the net photocurrent generated from incident unit light power, which can be expressed as the following [31][32] :…”

“…Another important factor is the defect and recombination center in materials. The long capture and release process of photocarriers from it influence carrier transport efficiency and response speed of PD significantly [31,37] .…”