Mapping of contactless photoelectrochemical etched GaN Schottky contacts using scanning internal photoemission microscopy—difference in electrolytes

Abstract

We present the experimental results on mapping characterization of n-type GaN Schottky contacts with selective contactless photoelectrochemical (CL-PEC) etching by using scanning internal photoemission microscopy (SIPM). The CL-PEC etching was performed in four kinds of aqueous solutions (KOH mixed with K2S2O8 (oxidant), phosphoric acid mixed with oxidant, only oxidant, and ammonia). The Schottky barrier height (qΦB) values decreased by less than 0.1 eV in the etching with the KOH and oxidant solutions. On the other hand, the opposite trend was observed for the samples etched with the phosphoric acid solution. Whereas the samples etched with the ammonia solution had a scattered qΦB value, they were not affected by the etching. However, the photoyield increased by 2.5 to 3.5 times in all kinds of etching. SIPM was found to be sensitive in visualizing the effect of the CL-PEC etching as an image.

Characterization of peripheries of n-GaN Schottky contacts using scanning internal photoemission microscopy

“…Such a large Y region on a periphery has been frequently observed in metal-mask samples. 14,26,39) In the metal-mask sample, the SIPM Y signal increased on the electrode periphery due to multiple reflections in the very thin metal layer. Since this phenomenon is not a simple internal photoemission process, a photoyield spectrum does not follow the Fowler's equation.…”