Characterization of deep levels at GaAs/GaAs and GaAs/InAs interfaces grown by MBE-interrupted growth technique

In order to find the origin of crystalline defects occurring in the preparation of InAs/GaAs quantum dots (QDs), their appearance was tracked through three different sample types designed as Schottky diodes. Specimens with a GaAs cap layer on a GaAs buffer layer as well as with an InAs wetting layer without QDs were grown by molecular beam epitaxy (MBE) using the interrupted growth technique. Deep level transient spectroscopy (DLTS) was used for comparison with structures containing InAs QDs. It was found that two main levels with thermal activation energies of 0.14-0.16 eV and 0.46-0.52 eV from the conduction band edge, respectively, are grown-in defects, which are characteristic of the growth interrupted interface occuring under an excess of As. Both these levels together with an additional level at 0.10-0.12 eV found in the InAs wetting layer structures were also present in those with QDs, probably resulting from strain or In penetration. All three defects were agglomerated close to the interface created by the interrupted growth. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)