Highly Strained InAs x P 1-x /InP Quantum wells Prepared by Flow Modulation Epitaxy
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HIGHLY STRAINED InAsxPl.X/InP QUANTUM WELLS PREPARED BY FLOW MODULATION EPITAXY
R. P. SCHNEIDER, Jr. AND B. W. WESSELS Department of Materials Science and Engineering and Materials Research Center Northwestern University, Evanston, Illinois 60208
ABSTRACT Flow modulation techniques have been used to prepare highly strained InAsxPlx/InP quantum well structures in an atmospheric pressure organometallic vapor phase epitaxial reactor. The compositions of the pseudomorphic wells ranged from x-0.40 to 0.74, corresponding to biaxial compressive strains of 1.3-2.4%. Well thicknesses ranged from 2 to 26 monolayers. The flow modulation growth conditions were found to have a strong influence on interface formation in the wells. For wells grown under optimized modulation conditions, low-temperature photoluminescence spectra revealed peak-splitting of the emission from the thinnest wells. This splitting is attributed to emission from regions in the wells with atomically smooth interfaces over areas greater in lateral extent than the exciton diameter. The full-width at half-maximum of the peaks is in the 6-15 meV range, comparable to the best reported values for latticematched InGaAs(P)/InP quantum wells grown by any technique, and is independent of well thickness or composition.
INTRODUCTION Semiconductor heterostructures with atomically abrupt interfaces are of considerable importance for device applications. Preparation of abrupt interfaces in the InGaAsP/InP quantum well system is particularly difficult because intermixing occurs on the group V sublattice during growth. Nevertheless, photoluminescence (PL) features attributed to emission from wells with atomically smooth interfaces was recently observed for lattice-matched InGaAs/InP [1] and InGaAsP/InP [2] quantum wells grown by organometallic vapor phase To minimize intermixing at the interface, flow rate modulaepitaxy (OMVPE). tion or low-pressure growth techniques were used. The preparation of abrupt interfaces in highly lattice mismatched systems is even more challenging because the lattice mismatch may result in misfit dislocation formation [3] and three-dimensional (island) growth [4,5]. We have recently reported the OMVPE growth of highly strained InAsP/InP multiple single quantum wells (SQW) with atomically abrupt interfaces, as indicated by PL peak splitting [6]. These strained InAsP/InP structures are of interest for a number of optoelectronic applications. The wavelength range of this system is tunable over the 1.3-1.6 pm range by varying the pseudomorphic well dimension and composition. In addition the detailed emission characteristics can be effected by varying the strain in the structure [7,8]. In the current study, we describe the growth of InAsxPlx/InP strained quantum wells by flow modulation epitaxy. Flow modulation was used to minimize interface roughness as well as intermixing at the interface. The interface is shown perfection was evaluated using photoluminescence spectroscopy. It that through proper choice of flow modulation conditions, highly strai
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