GaAs and AlGaAs crystallographic etching with low-pressure chlorine radicals in an ultrahigh-vacuum system

Abstract

GaAs and AlGaAs have been crystallographically etched with low-pressure chlorine radicals in an electron-cyclotron resonance (ECR) plasma shower with a new reactive-ion-beam etching (RIBE) system for obtaining damage- and contamination-free etching. The etching begins abruptly at 190 °C and increases gradually above 200 °C. The typical etching rate of a (001) plane is 1 μm/min at a substrate temperature of 300 °C. Mesa-shaped and reverse mesa-shaped grooves with {111}A side wall planes are obtained for 〈1̄10〉- and 〈1̄1̄0〉-oriented line and space masks. For square masks with [110] edge lines, on the other hand, high aspect-ratio columns with {100} vertical side wall planes are obtained. These results show that the etching rate of {111}A is much lower than that of {100}, {110}, or {111}B. AlGaAs is etched similarly to GaAs. Cl2 gas (not plasma excited) performs similar etching. However, the substrate temperature must be about 100 °C higher for the beginning of etching than for the Cl radical etching. These etching technologies are promising for microfabrication of GaAs/AlGaAs optoelectronic devices, replacing conventional wet chemical etching.