High-Resolution Scanning Electron Microscopy Observation of Electrochemical Etching in the Formation of Gate Grooves for InP-Based Modulation-Doped Field-Effect Transistors

Abstract

We show that during the wet-chemical formation of gate grooves for InAlAs/InGaAs-heterojunction-based modulation-doped field-effect transistors, the etching rates of InGaAs and InAlAs can be significantly modified by the exposure of the non-alloyed ohmic electrodes to citric-acid-based etchant. The presence of a Ni surface metal enhances the recess etching rate to a degree that is much higher than that in its absence. The presence of a Pt surface metal, however, causes this originally non-selective etchant to preferentially etch InGaAs over InAlAs. This selective etching behavior is attributed to the excess oxidation of InAlAs induced by the high electrode potential of Pt via an electrochemical effect. This study reveals the important impacts of electrochemical etching on the fabrication of gate recess grooves.