BROMINE-METHANOL AS AN ETCHANT FOR SEMICONDUCTORS - A FUNDAMENTAL-STUDY ON GAP .1. ETCHING BEHAVIOR OF N-TYPE AND P-TYPE GAP

Electrochemical and etching experiments were performed at n- and p-type GaP single crystals in the commonly used etchant bromine-methanol to investigate the fundamental aspects of the etching reaction. The etching properties of these methanolic bromine solutions were similar to those of bromine solutions in which water is used as the solvent; thus, e.g., as in water, the etching kinetics and morphologies at the (111) and (111BAR) faces are markedly different. In many cases of practical etching, methanol may be substituted by water as the solvent for bromine. The results allow us to propose an overall reaction equation f or the etch process as well as a detailed mechanism involving radical decomposition intermediates of the semiconductor. These intermediates may further react chemically either with species formed in the etch process itself or with ligands from the solution.