<title>Graded-effective-index waveguiding structures fabricated with laser processing</title>

Dopant-selective photoenhanced wet etching of GaN

“…Previous work on the PEC etching of GaAs has shown that rapid photoenhanced etch rates are achievable for n-type GaAs, while negligible etching occurs for p-type material. [13][14][15] The mechanism for dopant-selective etching is believed to arise from the very different chemical reactions occurring at n-type and p-type surfaces. The surface reactions are influenced by the "surface band bending" that occurs for semiconductors with different doping and the resulting behavior of photogenerated minority carriers in the near-surface region.…”

“…[12][13][14][15] The etching is enabled by the photogeneration of electron-hole pairs at the semiconductor surface which enhance the oxidation and reduction reactions in an electrochemical cell. Previous work on the PEC etching of GaAs has shown that rapid photoenhanced etch rates are achievable for n-type GaAs, while negligible etching occurs for p-type material.…”

UV-photoassisted etching of GaN in KOH

“…[1][2][3][4][5][6][7][8] The mechanism for photoenhanced etching involves the creation of e-h pairs, the subsequent oxidative dissociation of the semiconductor into its component elements (a reaction that consumes the photo-generated holes) and the reduction of the oxidizing agent in the solution by reaction with the photo-generated electrons. Generally, ntype material is readily etched under these conditions, while p-type material is not due to the requirement for confining photo-generated holes at the semiconductor-electrolyte interface.…”

Photoelectrochemical Etching of InxGa1−xN

“…These films are degenerately ntype (~ 10 20 cm -3 ) due to residual defects or impurities. Ti metal contacts were patterned by liftoff on the periphery of the samples, and etching performed in a standard electrochemical cell consisting of a teflon sample holder and a Pt wire cathode [2][3][4][5][6][9][10][11][12][13][14]. An unfiltered 450W Hg arc lamp ~ 15cm from the sample provided illumination of the samples, which were immersed in unstirred KOH, NaOH or H 2 O/AZ400K solutions.…”

“…It has long been recognized that the dissolution rate of semiconductor materials may be enhanced in acid or base solutions by illumination with above bandgap light [10][11][12][13][14]. The basic mechanism for their photo-enhanced etching is oxidative dissociation of the semiconductor into its component elements (thereby consuming the photogenerated holes) and the subsequent reduction of the oxidizing agent in the solution by reaction with the photogenerated electrons.…”