Open AccessHigh-Efficiency and High-Quality Photogalvanic Etching of the Silicon Doped N-Type Gallium Nitride Using Potassium Peroxomonosulfate Oxidant
Author(s) -
Sai Guo,
Mingming Zhang,
Liqing Qiao,
Huiqing Hu,
Kang Shi
Publication year - 2022
Publication title -
ecs journal of solid state science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.488
H-Index - 51
eISSN - 2162-8777
pISSN - 2162-8769
DOI - 10.1149/2162-8777/ac6907
Subject(s) - materials science , etching (microfabrication) , wafer , electrolyte , doping , optoelectronics , reactive ion etching , gallium nitride , nanotechnology , layer (electronics) , chemistry , electrode
Photogalvanic etching, or photo-assisted electroless etching, is a simple wet-etching approach to fabricate n-type gallium nitride (GaN)-based devices without any external power supply. However, the current technology is far from practical because efficient etching can only be realized by a potassium persulfate (PS) oxidant/alkaline electrolyte system that inevitably bends the etching surface. In this study, we proposed and tested a new potassium peroxomonosulfate (PMS) oxidant/weak acid electrolyte system for the photogalvanic etching of platinum (Pt) photo-mask patterned GaN wafers. A novel finding is that Pt can catalyze PMS decomposition in acids, predominantly generating singlet oxygen (1O2), whose onset reduction potential is 0.95 V higher than PS. Under 25.4 mW.cm2 ultraviolet (UV) irradiation, PS-driven photogalvanic etching of inert silicon-doped GaN (si-GaN) wafers is invalid, whereas the new system enables high efficiency and quality etching in 20 mM PMS+0.1 M K2SO4 electrolyte (pH=3.0). The etching rate reaches 12.0 nm.min-1, while the as-prepared groove bottoms have nanometer surface flatness, and the surface roughness (Ra) attains 5.25 nm (5x5 µm2). In summary, the PMS/weak acid electrolyte system makes photogalvanic etching is a promising practical technique.