Observation and control of electrochemical etching effects in the fabrication of InAs∕AlSb∕GaSb heterostructure devices

Abstract

In the fabrication of InAs∕AlSb∕GaSb heterostructure devices, the etching characteristics of Sb-bearing materials were observed to be significantly modified through electrochemically induced effects arising from the use of metal etch masks during etching in dilute ammonium hydroxide. Samples with different etch mask materials, such as SiNx, Ti, Cr, Ni, Pt, and Au, exhibited markedly different etching characteristics. In comparison to an insulating SiNx mask, etch masks with Au as the surface metal enhance the etch rate by factors of 2 and 7 in the vertical and lateral directions, respectively. The increase in etch rate depends strongly on the choice of the surface metal of the etch mask; higher etch rates were experimentally observed for surface metals with larger standard electrode potentials. The observed trends are consistent with interplay between electrochemical reaction and reaction rate kinetics in the etch solution. The electrochemical features of the etch process provide a potentially useful means for controlling the etch profile and may be useful for achieving enhanced device performance.