ODMR of Shallow Donors in Zn-Doped Lec-Grown InP
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ODMR OF SHALLOW DONORS IN Zn-DOPED LEC-GROWN InP
J. M. TROMBEYITA* AND T. A. KENNEDY Naval Research Laboratory, Washington, DC 20375
ABSTRACT ODMR spectra observed while monitoring the shallow donor-shallow acceptor pair emission in Zn-doped LEC-grown InP display strong features in the region near the conduction electron value of g=1.20. In addition to a previously observed narrow line, we observe a much broader resonance which dominates at low photoexcitation intensity. This broader line is interpreted as the unresolved exchange split resonances of electrons bound to residual shallow donors. The exchange broadening arises from interactions with nearby paramagnetic centers. Both resonances result in a decrease in the shallow-donor-to-shallow-acceptor radiative recombination and give evidence for pair recombination processes which compete with this emission.
INTRODUCTION Recombination in bulk semiconductors is generally influenced by the presence of defects. The use of ODMR (Optically Detected Magnetic Resonance) has, in many cases, identified a participating deep level species through signature structure such as a strong hyperfine interaction[ 1,2]. In contrast, only a few shallow centers have been unambiguously identified by this technique. One such example is the In donor in ZnO[3]. In several II-VI semiconductors, ODMR has been utilized to study the electron-hole exchange interactions present in donor-acceptor close-pair recombination[4,5]. Recently, an extensive optically detected electron nuclear double resonance study has demonstrated the effective-mass-like character of a donor in GaP[6]. Shallow donor magnetic resonance in InP has received limited attention to date. The theoretical g-value obtained by Lawaetz[7] using k-p perturbation theory is g = 1.20. A narrow electron paramagnetic resonance line with g = 1.20 was observed in slightly n-type InP by Goltzene et al.[8] and ascribed to residual shallow donors. In two recent observations a very narrow conduction electron spin resonance at g = 1.2042 ± 0.0005 has been assigned to electrons in a shallow donor impurity band[9,10]. The resonance of conduction electrons has also been observed through the polarization of photoluminescence in epitaxial n-type InP[ 11]. The g-value of shallow electrons is thus well understood and distinct due to its considerable shift from the free electron value of 2.0023. An early ODMR observation of a narrow line (20mT) near this g-value was made by Yan Dawei etal.[12] in a study of InP:Mn. This feature was assigned to electrons either in the conduction band or bound to donors. Robins et al.[ 13] observed a similar feature in LEC-grown InP:Zn. Both of these works emphasized deep centers. In this work we report a detailed study of two donor-like resonances observed in lightly Zn-doped InP. The new resonance, which is strongly inhomogeneously broadened, can be assigned to electrons bound to residual shallow donors. The dependence of these resonances upon photoexcitation intensity, microwave modulation frequency, and other parame
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