Selective Etching of 6.1 Å Materials for Transfer-Printed Devices

To enable the micro-transfer printing of GaSb-based multijunction solar cells, we explored methods to maximize etch selectivity between InAsSb and AlGa(As)Sb layers lattice matched to GaSb. We report the etch rates and morphology of InAsSb and AlGa(As)Sb in dilute HF and citric acid solutions. Etch solution temperature and composition were varied to maximize the etch selectivity between the etch stop layer and sacrificial layer. We found a mixture of citric acid and hydrogen peroxide yielded the highest etch selectivity ratio, 852.3, between InAsSb and AlGa(As)Sb. We additionally found that unlike higher fractions of Al, Al
0.34
GaAs
0.03
Sb did not appear to oxidize in dilute concentrations of HF and citric acid solutions, making it suitable as an etch stop layer.