Correlation of the 0.8 eV Emission Band with the EL6 Center in GaAs
- PDF / 247,217 Bytes
- 5 Pages / 420.48 x 639 pts Page_size
- 27 Downloads / 156 Views
Correlation of the 0.8 eV emission band with the EL6 center in GaAs S. ALAYA, M.A.ZAIDI*, G. MARRAKCHIa), H.MAAREF* H.J. VON BARDELEBEN "and J. C. BOURGOIN** *Facult6 des Sciences, Monastir 5000 TUNISIA **Groupe de Physique des Solides de LENS, Centre National de la Recherche Scientifiqueb), Tour 23, 2 place Jussieu Paris Cedex 05 -75251. FRANCE
ABSTRACT Combined photoluminescence and DLTS investigations of semi-insulating and n-type GaAs before and after a 15min, 8500C heat treatment under AsH 3 reveal that the treatment which anneals the EL6 center leads also to a disappearence of the 0.8eV PL band. The suggested correlation between EL6 and the 0.8eV PL is confirmed by the determination of the electron capture barrier of EL6 and the Franck-Condon shift deduced from the temperature dependence of the PL band leading to a consistant Configuration Coordinate diagram of this defect. I.INTRODUCTION The electrical characteristics of a semiconductor such as its free carrier concentration, mobility and minority carrier lifetime are determined by the interplay of the electrically active point defects. In the case of undoped semiconductors, such as the technologically important semi-insulating (S.I.) GaAs, this role is taken by the native defects [1]. Numerous defects have been detected in this material. The so-called EL2 center, commonly considered to be the most important defect in GaAs because of its strong influence on the electrical properties of the material, has been extensively studied [ 2 ] and was found to be present in all bulk-grown GaAs. The EL6 center at E -0.35eV [ 3 ] which is commonly seen in both Liquid Encapsulated
Czochralski
(LEC)
and Horizontal Bridgman
( H.B)
grown
GaAs,
has received much less attention. Deep Level Transient Spectroscopy (DLTS) measurements have allowed to determine its thermal activation energy E -0.35eV and its photoionization threshold of 0.8eV is obtained by optical excitation of DLTS (DLOS) [ 4 1. The large difference between the electron thermal activation energy and the photoionization threshold is explained by an abnormally large lattice relaxation. To our knowledge, no photoluminescence studies of the EL6 defect have been reported. Windscheif et al [5] reported a 450°C annealing step for the 0.8eV PL and attributed it from this to the EL2 defect. This is however incorrect as shown by the high thermal stability of the AsGa defect up to 1200 0C. The apparent disappearance of the charged ASGa defect in neutron irradiated SI GaAs being due to a Fermi level shift. A different aspect, which we have not studied here, is the defect profile of EL6 and the 0.8eV PL into the bulk. Our study was limited to the correlation of EL6 and the 0.8eV PL in the near surface region. II- EXPERIMENTAL Samples used in the present work were SI and n-type bulk GaAs. The n-type samples were Se doped LEC and Si doped HB grown crystals with a carrier concentration of the order of 101 7 cm-3 . The semi-insulating samples were grown by the LEC method.
a) present adress: Laboratoire de physique de l
Data Loading...
