Electron Paramagnetic Resonance Study of Low Temperature Molecular Beam Epitaxy Grown GaAs and InP Layers
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ELECTRON PARAMAGNETIC RESONANCE STUDY OF LOW TEMPERATURE MOLECULAR BEAM EPITAXY GROWN GaAs and InP LAYERS H.J.von Bardeleben*,Y.Q.Jia*, J.P.Hirtz'*, J.C.Garcia*", M.O.Manasreh** ,C.E.Stutz ***,K.R.Evans*** *Groupe de Physique des Solides, Universit6 Paris 7, 2 place Jussieu, 75251 PARIS Cedex France **THOMSON CSF, Laboratoire Central de Recherches, Domaine de Corbeville, 91404 ORSAY France .**Electronic Technology Directorate (WL, ELRA), Wright -Patterson Air Force Base, DAYTON, Ohio 45433-6543, USA ABSTRACT The native defects in LTMBE III-V layers have been studied by the electron paramagnetic resonance (EPR) technique for three different systems: GaAs on GaAs, GaAs on Si and InP1on 9 InP. The GaAs layers are characterised by high concentrations of ionized arsenic antisite defects(10 cm -3 with the growth GaAs. Their variation ), with properties similar to those of the native AsGa in amorphous temperature, layer thickness and thermal annealings has been assessed . The results are independant on the nature of the substrate, GaAs or Si. Inspite of a 1%phosphorous excess no phosphorous antisites could be detected in the as-grown, undoped or Be doped InP layers.
1. INTRODUCTION: Semi-insulating undoped GaAs layers grown by the low temperature molecular beam epitaxy on GaAs substrates have been shown to have interesting technological applications, ranging from buffer layers in GaAs based MESFET,MODFET and HEMT structures to the application in ultrafast detectors due to small minority carrier lifetimes [1]. The electical[2,3] and optical [4,5]properties of these layers are 0 quite distinct from those obtained by "classical" high temperature MBE layers grown in the 600 C temperature range. Whereas these layers are characterised by low native defect concentrations (= 1014 cm- 3 ), the LTMBE layers contain native defects in the 1019 cm" 3 concentration range. Among
them only an arsenic antisite related defect has been identified [6,7], as in the case of meltgrown GaAs, where the semi-insulating properties are equally related to an arsenic antisite related defect, EL2[8]. LTMBE GaAs layers with these particular properties can only been grown in a limited temperature range at 200°C, as for lower temperatures polycrystalline or amorphous layers are formed and for higher temperatures the defect concentraztion diminuishes rapidly. The as-grown layers are highly instable to thermal annealing and in fact due to their low electrical resistivity would not be of interest in the above cited applications. Itis only in the annealed state, which is often implicitly obtained 0 by active layer overgrowth in the 600 C temperature range, that the layers are of high electrical resistivity (>106 cm).
For an optimisation of growth conditions and post growth treatments of these layers an analysis of the native point defects is of interest. Thus we have undertaken an electron spin resonance (EPR) study of the defects in LTMBE GaAs layers grown on GaAs substrates as a function of growth temperature sample thickness as well as furnace annealing
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