The study of wet etching on GaN surface by potassium hydroxide solution

Abstract

Potassium hydroxide solution was used to etch un-doped GaN grown on the sapphire substrate at 180 and 260°C. We illustrated the etching phenomenon in detail and probed its mechanism in the wet etching process. By multiplying the planar density and the number of dangling bonds on the N atom, we proposed the etching barrier index (EBI) to describe the difficulty degree of each lattice facet. The raking of EBI will be ?cCombining the EBI with SEM results, we thoroughly studied the whole etching process. We confirmed that in our research, KOH wet etching on GaN starts from the r-plane instead of the ?c-plane or -c-plane, which differs from other studies. We also found that during the high-temperature etching process, there are two etching approaches. In one, the etching begins vertically from the top to the bottom, then horizontally, and finally reversely from the bottom to the top. In the other, etching pits will develop into a hexagonal hole of the sidewall of m-plane.

Enhanced Light Extraction of Flip-Chip Mini-LEDs with Prism-Structured Sidewall

“…Surfaces with high density of N dangling bonds possess large repulsion to the hydroxide ions, which stops the crystallographic etching at such surface [29]. The density of N dangling bonds on different GaN lattice planes can be ranked as follows: (0001) plane > (1-210) plane > (10-10) plane > (000-1) plane [30]. Thus, the (0001) plane and (1-210) plane have larger repulsion force to the hydroxide ions, and the TMAH etching did not proceed on the top surface and the sidewall along [10-10] direction under our experiment condition.…”

On-wafer fabrication of cavity mirrors for InGaN-based laser diode grown on Si

“…in ref. 30 to describe the etching resistivity of each GaN plane in alkaline etching solution. The higher the EBI of the plane is, the more difficult the etching of the plane would be.…”

Revealing the Role of Sidewall Orientation in Wet Chemical Etching of GaN-Based Ultraviolet Light-Emitting Diodes

“…Without the aid of UV light irradiation or bias voltage, the wet etching only selectively occurs at semi-polar and non-polar planes of GaN, which would not prohibit the hydroxide ions from accessing the Ga atom [22,23,24]. It was also reported that the wet etching rate of GaN is dependent on the crystallographic planes of GaN [25,26,27]. Thus, the anisotropic wet etching of GaN generally leads to peculiar textures at different surfaces, such as trigonal prisms and hexagonal pyramids, by exposing specific crystallographic planes [21,28,29].…”