Mocvd Growth and Properties of Erbium Doped GaAs
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MOCVD GROWTH AND PROPERTIES OF ERBIUM DOPED GaAs
DIETRICH W. LANGER-, YABO LI', XIAO M. FANG" AND VICTORIA COON" *Electrical Engineering Department, University of Pittsburgh, Pittsburgh, PA 15261 "'Microtronics Associates, Inc., 3337 Forbes Ave., Pittsburgh, PA 15213 ABSTRACT Erbium doped GaAs was grown by metalorganic chemical vapor deposition using a novel liquid precursor: Tris(n-butylcyclopentadienyl)erbium, Er(C4H9 C5 H4)3. Growth parameter, i.e. temperature, V/III ratio, Er-vapor flow, were investigated. The maximum erbium incorporation in layers with excellent morphology was 1.2x 1019cm 3 . The erbium-related photoluminescence intensity and the incorporated concentrations, as measured by secondary ion mass spectrometry, were correlated. Based on a simple model for ,the excitation dependence of the emission, the non-radiative Auger-type process was estimated to be nearly five times that of the energy transfer process from bound excitons to the Er3 + ions, which subsequently resulted in the Er-related light emission. Temperature induced quenching of the emission was found to be dominated by transitions with an activation energy of 74meV. INTRODUCTION Erbium-doped GaAs is one of the materials which has been studied intensively because its sharp and temperature-independent 4f-intrashell emissions around 1.54/im matches the wavelength of lowest attenuation of silica-based optical fibers." 5 It has been reported that the erbium-related emission lines around 1.54gum are contributed by erbium complexes incorporated into several different sites in GaAs crystal structures.",3 Unlike its ytterbium counterpart, Er3 + ion in GaAs has been found to reside either at a cation site or an interstitial site depending on growth procedures. 2'" Attention has been paid to the selective formation of specific RE centers in semiconductor hosts to fully utilize all the optically active RE trivalent ions available. Metalorganic chemical vapor deposition (MOCVD) has been used in the growth of erbium-doped GaAs crystals with simple and reproducible spectra.' In the past, several erbium source materials have been utilized.3' 6 As demonstrated in previous studies, liquid precursors of erbium metalorganic compounds are preferable to solid ones because of their high vapor pressures and doping controllability. In this paper we present the results on the growth of erbium-doped GaAs by MOCVD using a new liquid source which contains besides erbium only carbon and hydrogen, elements which are anyway abundant in the growth process. We used Tris(n-butylcyclopentadienyl)erbium [Er(C 4H9C5 H4)3], commercially available from Strem Chemicals, Inc.. The dependence of erbium concentration in GaAs epilayers on the growth temperature, V/III ratio and the hydrogen (H2) flow rate through the erbium bubbler has been investigated. The grown samples have been characterized by secondary ion mass spectrometry (SIMS) and photoluminescence (PL).
Mat. Res. Soc. Symp. Proc. Vol. 301. ©1993 Materials Research Society
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DESCRIPTION OF EXPERIMENTAL SETUP The MOCV
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