Study of Wet Chemical Etching of Al[sub x]Ga[sub 1−x]InP[sub 2] Films Using Hydrochloric Acid

Abstract

The etching behavior of Al x Ga 1−x InP 2 ͑0 ഛ x ഛ 1͒ in aqueous HCl was investigated for layers on their native GaAs substrates as well as for layers after releasing from their substrate and transferring to a foreign plastic carrier utilizing the epitaxial lift-off ͑ELO͒ technique. For InGaP 2 layers on their native substrates the activation energy of the etching rate was determined to be 22 kcal/mol for HCl concentrations of both 6 and 12 M. The surface roughness of the partially etched Al x Ga 1−x InP 2 layers as determined with atomic force microscopy ͑AFM͒ was found to decrease with increasing aluminum fraction and to be smaller for 6 M than for 12 M HCl. Al x Ga 1−x InP 2 layers on foreign plastic carriers were often found to be not etched in HCl, in contrast to layers on substrates. This could not be attributed to a single cause and it is suggested that the nonetching behavior is related to a combination of factors, like exposure of the layers to the ELO process and strain induced by the foreign carrier. AFM studies showed an increased density of irregularities at the surfaces of the Al x Ga 1−x InP 2 samples that later showed nonetching behavior.

On the development of high-efficiency thin-film GaAs and GaInP2 cells

“…An essential step in thin-film solar cell processing is mesa etching to reach the back contact metallization and to prevent short circuits on the edges of the cells. However, the etching behavior of thin-film GaInP 2 on a foreign carrier was found to be entirely different from that observed for GaInP 2 layers on their native substrate [8]. The encountered difficulties during etching is a bottleneck for the development of thin-film GaInP 2 cells.…”

“…20%) of the sample was covered with Apiezon black wax. Subsequently, the samples were immersed in aqueous HCl for some time to remove the GaInP 2 to a depth of maximally 0.4 mm [8]. The etching was performed in a glass beaker, which was put in a temperature controlled water bath.…”

Thin-Film III–V Solar Cells Using Epitaxial Lift-Off

“…This increased thickness can slow down the etch rate somewhat and thus increase the lift-off time, but this is normally not a problem. It was noticed that the InGaP etching behaviour for thin-films is not the same as for material on the wafer [38]. Therefore in the processing of the thin-film cells other etchants than HCl are preferred.…”

“…With today's record efficiency of 44.0% under a concentration of 942 suns [38] III-V solar cells have not reached their full potential. The multi-junction concept has the perspective of obtaining efficiencies above 45% and maybe even 50% under concentration.…”

Fabrication of ridge waveguide of 808 nm GaAs-based laser diodes by wet chemical etching

“…For the p-type GaAs cap layer, a variety of etchants are explored. In most GaAs etchants, the oxidizer is H investigated in References [17][18][19][20]. To simplify the technological process, a kind of appropriate etchant which can corrode simultaneously InGaP and AlGaInP layers is expected.…”