Effects of Ytterbium Addition on Liquid Phase Epitaxial Growth of InGaAs/InP Heterostructures
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Effects of Ytterbium Addition on Liquid Phase Epitaxial Growth of InGaAs/InP Heterostructures A. DAVIS, H.M. DAUPLAISE, J.P LORENZO, G.O. RAMSEYER*, AND J. A. HORRIGAN Rome Laboratory Hanscom Air Force Base, MA 01731 *Griffiss Air Force Base, NY 134.41 ABSTRACT We have investigated the effects of Yb addition to melts used for the growth of InGaAs/InP heterostructures by liquid phase epitaxy. Our results indicate that impurities in the Yb play an important role in determining the changes in electrical properties observed in the epilayers after Yb treatment of the melt. We have examined samples using double-crystal x-ray diffractometry, photoluminescence, Hall/van der Pauw measurements, and secondary-ion mass spectroscopy. After Yb treatment, the residual carrier concentrations of the epilayers were reduced by more than one order of magnitude and the samples luminesced more strongly; while the lattice matching and crystal quality of the epilayers were not measurably affected by the Yb. There was a smaller-thanexpected increase in the 77K mobility and a marked increase in the compensation ratio of the epilayers grown after the addition of Yb to the melt. We believe the Yb is both acting as a scavenging agent in the melt, combining with impurities that otherwise would have been incorporated in the epilayers, and introducing deep level impurities of its own, which are incorporated into the grown layers.
INTRODUCTION Past studies of rare-earth doping of semiconductors have focused primarily on the 4f-4f emiss: on line of the dopant, the wavelength of which is generally independent of the host material. Rare-earth luminescence has been seen in IIIV layers grown by liquid phase epitaxy (LPE), metalorganic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE) [1-3]. The addition of rare-earth elements to epitaxial growth sources has also been reported to dramatically improve the electrical properties of the resulting epilayers [4-7]. A reduction in residual carrier concentration was also observed after rare-earth addition to bulk InP crystals grown by liquid-encapsulated Czochralski [8]. The addition of small amounts of r are-earth elements to LPE growth melts has been shown to reduce the length of the bakeouts that have typically been required to obtain residual carrier concentrations sufficiertly low to fabricate usable optoelectronic devices [4]. We have investigated the results of ytterbium addition to LPE melts used to grow InGaAs/InP heterostructures. The resulting epilayers were examined by double-crystal x-ray diffractometry (DCXRD), photoluminescence (PL), Hall/van der Pauw measurements, and secondary-ion mass spectroscopy (SIMS). We have compared samples grown before and after rare-earth addition to the melt. Our results indiate that im;'urities present in the Yb play a critical role in the observed electrical phenomena
Mat. Res. Soc. Symp. Proc. Vol. 301. ©1993 Materials Research Society
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EXPERIMENTAL The InGaAs layers were grown in a low-mass LPE system consisting of a slidirg, high-density
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