Re-entrant Layer-by-Layer Etching of GaAs(001)

TL;DR

This paper reports the first observation of re-entrant layer-by-layer etching of GaAs(001) using in situ measurements, revealing temperature-dependent regimes explained by atomistic simulations of etching kinetics.

Contribution

It introduces the first experimental observation of re-entrant layer-by-layer etching and provides a kinetic model explaining the temperature-dependent behavior.

Findings

Re-entrant layer-by-layer etching observed at specific temperatures.

Simulations reproduce the three temperature regimes.

Site-selectivity and activation barriers govern the etching process.

Abstract

We report the first observation of re-entrant layer-by-layer etching based on {\it in situ\/} reflection high-energy electron-diffraction measurements. With AsBr$_3$ used to etch GaAs(001), sustained specular-beam intensity oscillations are seen at high substrate temperatures, a decaying intensity with no oscillations at intermediate temperatures, but oscillations reappearing at still lower temperatures. Simulations of an atomistic model for the etching kinetics reproduce the temperature ranges of these three regimes and support an interpretation of the origin of this phenomenon as the site-selectivity of the etching process combined with activation barriers to interlayer adatom migration.