Photoenhanced wet etching of gallium nitride in KOH-based solutions

Abstract

Photoelectrochemical etching (PEC) of n+-GaN in KOH and AZ400K photoresist developer is presented. We compare the two solutions used for PEC etching without an external bias. The influence of etchant concentration and of the intensity of ultraviolet illumination was studied with emphasis on the resulting etched surface quality. The quality of the shallow etched surface and its roughness are presented. The AZ400K etchant was applied to shallow etching of n+-GaN with threading dislocation densities in the range of 109–1010 cm−2. Moreover, the first analysis of photocurrent monitoring during the electrochemical etching of GaN epitaxial layers in KOH is presented. We found that photocurrent very sensitively reflected the changes in the quality of the etched surface.

Influence of Electrochemical Etching on Electroluminescence from n-Type 4H- and 6H-SiC

“…A defect-free material is important for electronic devices. Defects may be introduced during crystal growth or by polishing ͑mechanical or chemomechanical͒, sputter etching, 5,6 or handling. Luminescence measurements give information about defects in semiconductors.…”

Thermal doping of rare-earth ions in gallium nitride

“…Samples were lightly etched in a 2 M aqueous solution of potassium hydroxide (KOH) for 20 min with brief agitation. This process was carried out under ultraviolet (UV) illumination from a mercury discharge lamp [18]. The incident radiation was mainly centred at a wavelength of 320 nm.…”

Wet chemical etching of Al 0.65 Ga 0.35 N in aqueous KOH solutions

“…The mechanism of wet etching of GaN was illustrated to be the formation of an insoluble coating of presumably gallium hydroxide (Ga(OH) 3 ) and the subsequent dissolving in different solvents 14,16,18,23 . Many methods are used to characterize the etched surface, including scanning electron microscopic (SEM) [12][13][14][16][17][18][19][20][21]23,26,27,[29][30][31] , atomic force microscopy (AFM) 8,24,27 , transmission electron microscopy (TEM) 19,21,22 , x-ray photoelectron spectroscopy (XPS) 28 , Auger electron spectroscopy (AES) 23 , energy-dispersive x-ray analysis (EDX) 18 , x-ray diffraction (XRD) 18 , and spectroscopic ellipsometry (SE) 15 . A comprehensive review for wet chemical etching of GaN, AlN, and SiC has been presented by D. Zhuang and J. H. Edgar 5 .…”

“…In addition to these dry etching methods, wet chemical etching processes have been proved to be effective techniques to avoid damages introduced in etching courses [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] . In order to achieve a suitable etch rate and smooth surface, photoelectrochemical (PEC) wet etching of GaN-based materials 14,[16][17][18][19]21,[23][24][25][26][27]29,30 , which was first demonstrated by Minsky et al 14 , has been studied extensively, especially by the groups of E. L. Hu and I. Adesida 14,16,17,19,21,25,29,30 . The mechanism of wet etching of GaN was illustrated to be the formation of an insoluble coating of presumably gallium hydroxide (Ga(OH) 3 ) and the subsequent dissolving in different solvents 14,16,18,23 .…”