Indium surface segregation in strained GaInAs quantum wells grown on ((1)over-bar (1)over-bar (1)over-bar) GaAs substrates by MBE

Surface segregation of indium during molecular beam epitaxy of Ga0.85In0.15 As/GaAs ((1) over bar (1) over bar (1) over bar) quantum wells is studied b y means of in situ X-ray photoelectron spectroscopy measurements. The inten sity ratio of In-4d/Ga-3d core-level spectra is used to precisely determine the amount of segregated Indium at the surface during the growth of GaInAs on GaAs substrates. GaAs ((1) over bar (1) over bar (1) over bar) substrat es exactly oriented and tilted 2 degrees toward [2 (1) over bar (1) over ba r] or [(2) over bar 1 1] have been investigated. The results are compared t o those obtained on (1 0 0) GaAs substrates. We show that the amplitude of the In segregation phenomenon is larger for the GaAs ((1) over bar (1) over bar (1) over bar) substrate tilted 2 degrees toward [2 (1) over bar (1) ov er bar] than for the other substrates investigated for growth temperatures ranging from 380 degrees C to 540 degrees C. Having determined by atomic fo rce microscopy the dependence of the terrace step structure of the GaAs ((1 ) over bar (1) over bar (1) over bar) surface with the direction of the sub strate tilt, we propose a kinetic explanation of our results. We show that an increase of the In segregation phenomenon is related to an increase of t he adatom diffusion length obtained by an increase of the growth temperatur e and/or a modification of the terrace step structure. (C) 1999 Elsevier Sc ience B.V. All rights reserved.