Selective Etching of Gallium Arsenide Crystals in Hsub 2SOsub 4-Hsub 2Osub 2-Hsub 2O System

Selective etching of GaAs in the H 2 SO 4 ‐ H 2 O 2 ‐ H 2 O system was studied as a pretreatment to selective deposition. Flat‐bottomed holes were obtained in low H 2 SO 4 solutions, whereas nonplanar holes were obtained in high H 2 SO 4 solutions. Differences between both cases are considered from the etching behaviors under nonselective conditions. Using low H 2 SO 4 solutions, selective etching was conducted on substrates with different crystallographic orientations. Asymmetrical holes were observed in all cases except for holes on the 001 substrate with rectangular windows held parallel to the 〈001〉 direction. The possibility of the revealed planes being the wall in the hole is discussed.