Development of selective lateral photoelectrochemical etching of InGaN/GaN for lift-off applications

Abstract

The authors have developed a wet band gap-selective photoelectrochemical etching process to produce deep undercuts (∼500 μm) into InGaN/GaN heterostructures. These undercuts were used in a lift-off process which successfully transferred device-scale (100 μm diameter, 5 μm thick) disks from their underlying sapphire substrates to another substrate. Experiments were conducted using a lamp-and-filter arrangement, employing n-type and p-type GaN pieces as filters. Polishing was conducted to smooth the resulting substrate-transferred GaN disks.

Dislocation- and crystallographic-dependent photoelectrochemical wet etching of gallium nitride

“…Photoenhancement of a wet chemical etch has proven to be a useful tool in the fabrication and analysis of group IIInitride materials. Above band-gap illumination of III-nitrides immersed in electrolytes such as KOH has resulted in substantial augmentation of etch rates in both the vertical and lateral directions, 1 allowing the formation of electronic, 2 optical, 3 and mechanical devices. 4 In general, photoenhanced wet etching of semiconductors depends on the wavelength and intensity of the illumination source, the nature of the electrolyte, and the doping and band gap of the semiconductor.…”

Observation of high Q resonant modes in optically pumped GaN/InGaN microdisks fabricated using photoelectrochemical etching

“…These devices have shown rather broad, low Q emission and required high pump power densities (25 kW/cm 2 average power from a picosecond excitation source) [4,5]. Using bandgap selective photoelectrochemical (PEC) etching [6,7], we have fabricated mushroom-shaped GaN disks with InGaN active regions which exhibit high Q values from 1700-2700. The bandgap-selective PEC etching allows for better optimization of the microdisk structure, allowing single mode vertical confinement, and isolation of the WGMs from neighboring materials.…”

Current Apertured Vertical Electron Transistor (CAVET)

“…The imagined structure of device is shown in Fig Id. Photoelectrochemical wet etching [10,11] has been an efficient way to selectively etching InGaN (lower bandgap material) over GaN(higher bandgap material). The principal issues here regard achieving a sufficiently smooth etched surface.…”