REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION OBSERVATION OF ANION-EXCHANGE REACTIONS ON INAS SURFACES

We have used time-resolved reflection high energy electron diffraction (RHEED) measurements to study anion exchange reactions in molecular b eam epitaxy (MBE) grown III-V semiconductors. In the experiment, InAs surfaces are exposed to Sb, fluxes and subsequent changes in the cryst als RHEED patterns are examined. We find that when an InAs surface is initially exposed to an Sb flux the specular spot intensity first decr eases, then recovers back toward its initial value. The shape of the i ntensity versus time curves is extremely reproducible if the absolute Sb flux and the Sb species are kept constant. The length of time requi red for the RHEED pattern to stabilize is much shorter for cracked Sb than for uncracked Sb. The RHEED dynamics are also faster if the total Sb flux increases. The behavior of the RHEED dynamics as a function o f Sb flux and Sb species is consistent with the changes in the RHEED p attern being due to an Sb/As exchange reaction on the crystal's surfac e, The RHEED data are compared to previously published x-ray photoelec tron spectroscopy (XPS) data which studied exchange reactions on InAs surfaces exposed to Sb fluxes. The XPS study confirmed that the incide nt Sb did indeed exchange with As in the epilayer and estimated the ex posure time needed to complete the Sb/As exchange reaction. The time s cales for exchange associated with the RHEED and XPS data are in good agreement. This further indicates that RHEED could be used to indirect ly probe anion exchange reactions, potentially opening up several aven ues of research ranging from basic materials science to MBE process co ntrol in manufacturing.