Arsenic clusters on the surface of vertically aligned InAs islands on GaAs substrate by annealing

Abstract

The formation of arsenic clusters in a system of vertically aligned InAs quantum islands on GaAs during thermal annealing under As overpressure has been investigated by transmission electron microscopy (TEM) and Raman scattering. Semicoherent arsenic clusters, identified by TEM examination, have been formed on the surface of the GaAs capping layer. The existence of arsenic precipitates is also confirmed by Raman spectra, showing new peaks from the annealed specimen at 256 and 199 cm−1. These peaks have been ascribed to A1g and Eg Raman active phonons of crystalline arsenic. The phenomenon can be understood by a model of strain-induced selected growth under As overpressure.

Origin of two special Raman modes in dilute nitrides

“…Here we propose another assignment on the modes at 197 cm −1 and 255 cm −1 . In fact, the behavior of these two modes is in every aspect in agreement with that of elemental arsenic semimetals (rhombohedral, 3m point group) [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. The frequency of the peak A and B (197 cm −1 and 255 cm −1 ) for our GaAsN samples are close to that for the double degeneracy E g mode (195 cm −1 ) and the A g mode (257 cm −1 ) from crystalline arsenic.…”

“…The element can crystallize within the host matrix and/or at the surface [44,45]. The precipitation of As has been reported in low temperature grown GaAs after thermal annealing from 450 • C to 900 • C of different time lengths [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] and other As-containing alloys [40,55,56]. In these observations, shape, size and distribution of As crystalline domains varied with different annealing condition and composition of the host material.…”

“…It is known that the V element migrates to the surface under thermal treatment of III-V semiconductors. The element can crystallize within the host matrix and/or at the surface [44,45]. The precipitation of As has been reported in low temperature grown GaAs after thermal annealing from 450 • C to 900 • C of different time lengths [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] and other As-containing alloys [40,55,56].…”