A simple wet etch for GaN

Abstract

A simple UV photo-enhanced wet etch has been developed for GaN. Unlike photoelectrochemical wet etching, this technique does not require an electrical contact to be made to the sample, and nitrides deposited on insulating substrates (such as sapphire) can be etched. The technique relies on adding an appropriate oxidizing agent, in this case, peroxydisulfate to KOH solutions. Maximum etch rates are observed at pH 12.4. The etch rate increases linearly with light intensity at 365 nm up to intensities of 25 mW/cm 2 , where etch rates of up to 50 nm/min are observed.

Fabrication of p-type porous GaN on silicon and epitaxial GaN

“…Figures 1(e) and 1(f) show I-V curves taken from Mg-doped porous GaN grown from Auand Pt-coated Si (100) substrates, respectively. For samples grown using an Au catalyst, a near Ohmic contact behavior was repeatedly observed which is consistent with the formation of a Ga 2 Au intermetallic between the underlying substrate and GaN material 9 in a similar way observed for undoped porous GaN particles.…”

“…3 The formation of p-type porous GaN is particularly relevant 4 for the fabrication of junctions and active regions for GaN-based LEDs with improved light extraction efficiency and external quantum efficiencies by gradation of the effective refractive index. 5 Porous GaN has been typically fabricated by (photo)electrochemical and chemical etching methods, [6][7][8][9] predominantly a top-down etching of epitaxial GaN, giving textured surfaces as a result of pore coalescence and variations in etch rates for extended etching times. A range of nanoscale III-N materials 10,11 in arrays and assemblies spanning emission from the blue to red regions of the visible spectrum, 12 and white light emitting light emitting devices and multi quantum wells have also been realized.…”

The K2S2O8–KOH photoetching system for GaN

“…For revealing of defects in GaN, three main groups of selective etchants have, so far, been widely explored: (i) molten salts used at high temperature (260-480 1C) [1][2][3], (ii) hot sulfuric and phosphoric acids at 180 À250 1C [2,4] and (iii) dilute aqueous KOH solutions [5][6][7]. A promising improvement of the latter method was obtained by adding to KOH solution potassium peroxydisulphate (K 2 S 2 O 8 ), which considerably enhances etch rates [8][9][10][11]. In a recent paper, the details on the mechanism of reactions at the GaN surface in the KOH-K 2 S 2 O 8 solutions were discussed on the basis of electrochemical results [12].…”

Porosity-induced relaxation of strains in GaN layers studied by means of micro-indentation and optical spectroscopy

“…[16][17][18][19][20][21] In particular, the development of porous GaN structure offers a significant enhancement with regards to the thermal, mechanical, and chemical stability as well as the potential to blue-shift of the band gap further into the ultraviolet region. 22 The fabrication of porous GaN structure was first developed by Bardwell et al 23 by means of a metal-assisted electroless chemical etching technique. In a typical synthesis, an ultrathin Pt catalyst layer was deposited on the semiconductor where the exposed area was etched in a HF: CH 3 OH: H 2 O 2 solution.…”