The following papers will be presented at the 8th Biennial Workshop on OMVPE, on Wednesday morning, April 16th, 1997. The calendar of events describes the entire technical program.
R. Bhat, Bellcore, Red Bank, NJ 07701
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InAlGaAs QWs for Red Lasers: J.S. Roberts*, J.P.R. David*, P.M. Smowton**, and P. Blood**, *Department of Electronic and Electrical Engineering, University of Sheffield, Mappin St., Sheffield S1 3JD, UK; **Department of Physics and Astronomy, University of Wales College of Cardiff, P.O. Box 913, Cardiff CF2 3YB, UK
Laser diodes with emission in the wavelength range 700nm to 750nm are potentially important light sources for photodynamic therapy. In general, compressively strained InGaP QWs can not be extended above 700nm and AlGaAs devices show a degrading efficiency for wavelengths below 780nm. Using ultra pure alkyl reagents we have been able to prepare In x(Al 0.45Ga0.55)1-xAs QWs at 620C where the indium mole fraction is as high as 25%. These compressively strained single QWs on GaAs emit in 700nm to 750nm band and can be incorporated as the gain elements of laser diodes. Initially a photoluminescence study was undertaken to assess the range of wavelengths available with this new QW system. InAlGaAs QWs were prepared by the addition of In to Al0.40Ga0 60AS making the quaternary composition relatively simple to prepare by MOVPE. Test structures consisting of 4 QWs with 2000Å barriers were assessed by 10 K PL. In addition SWQ SCH lasers have been prepared with emission at 730nm and 748nm.
Self-Limiting OMCVD Growth of GaAs on V-Grooved Substrates with Application to InGaAs/GaAs Quantum Wires: Giorgio Biasol, Frank Reinhardt, Anders Gustaffsson, and Eli Kapon, Institut de Micro-et Optoelectronique, Departement de Physique, Ecole Polytechnique Federale de Lausanne, CH 1015, Lausanne, Switzerland
Growth of GaAs-AlGaAs quantum wires (QWRs) on V-grooves relies on the establishment of sharp V-shaped AlGaAs self-limiting profiles; GaAs overgrowth then results in the formation of a crescent-shaped QWR. We demonstrate that the QWR formation occurs via a transient increase of the growth rates in a set of different nanofacets, forming at the bottom of the groove. Upon growth of sufficiently thick layers on AlGa As, the GaAs surface reaches a self-limiting profile as well. This transition takes place through an equalization of the relative growth rates. Atomic force microscopy (AFM) studies show that the monolayer step distribution in the facets along the groove determines the relative incorporation rates, and therefore the facets extension. The GaAs profile is much broader than for AlGaAs at corresponding growth temperatures; however, it can be sharpened down to 5nm for T=550C. Under these conditions, GaAs was successfully used as a barrier material for self-ordered InGaAs QWRs. In particular, we report the formation of uniform, vertically stacked arrays of InGaAs/GaAs wires. Structural and optical properties of these QWR arrays will be presented.
1.15 Micron Strained-Layer InGaAs-GaAs-InGaP Buried Heterostructure Lasers Grown on Ternary InGaAs Substrates by Selective-Area MOCVD: A.M. Jones, A.H. Moore+, W.A. Bonner*, and J.J. Coleman, Microelectronics Laboratory, University of Illinois at Urbana-Champaign, 208 N Wright St. Urbana, IL 61801, +EG&G Canada, Ltd., Optoelectronics Division, Vaudreuil, Quebec J7V8P7, *Crystallod, Inc., Somerville, NJ 08876
For lasers based on GaAs substrates, the maximum attainable emission wavelength for InGaAs active regions is ~1.1 micron due to critical thickness constraints. This ceiling can be extended by utilizing low-composition ternary InGaAs substrates which enable emission wavelengths to approach the low-dispersion optical communication band around 1.3 microns. Previously reported results from broad area (W=150 microns) InGaAs-GaAs-InGaP lasers grown on ternary In0.03Ga0.97As substrates using conventional MOCVD demonstrate wavelength extension out to 1.14 microns. In this paper, the successful fabrication of strained-layer InGaAs-GaAs-InGaP buried heterostructure lasers grown on ternary In0.03Ga0.97As substrates is reported. Selective-area MOCVD is used to explore a wide range of InGaAs thicknesses and compositions. This is accomplished by depositing the QWs through an oxide growth mask whose dimensions vary across the wafer. The longest emission wavelength measured is 1. 1504 microns for the 3 micron wide active regions. The growth and fabrication details will be presented, and the partial strain compensation delivered by the tensile-strained GaAs barriers will be discussed.
MOVPE Growth of all-AlGaAs Visible (~700 nm) Vertical-Cavity Surface-Emitting Lasers: Hong Q. Hou, M. Hagerott Crawford, B.E. Hammons, and R.J. Hickman, Sandia National Laboratories, MS 0603, Albuquerque, NM 87185
To date, room-temperature continuous-wave (CW) operation of vertical-cavity surface-emitting laser (VCSEL) in the 650-700 run wavelength regime has only been reported for AlGaInP active regions. In this paper we present all-AlGaAs VCSEL as an alternative to AlGaInP-based VCSELs for the longer wavelength visible regime. Our studies include an extensive optimization of the photoluminescence intensity and doping efficiency (Si and C dopants) of AlGaAs as a function of the substrate misorientation. The laser active laser consisting of five Al0.24Ga0.76As(80 Å)/Al0.4Ga0.6As quantum wells were grown on misoriented (100) substrates with misorientation of 0, 2, 6, 10, 15 and 25° toward (111)A. A 2.5-fold improvement of PL efficiency is obtained for the samples grown on (311)A substrates (~25° misorientation) as compared to 2° off samples. Red VCSELs (~700 nm) consisting of p and n-type Al0.96Ga0.04As/Al0.4Ga0.6As distributed Bragg reflectors and A10.24Ga0.76As quantum wells were grown with a rotating-disk MOVPE reactor on (311)A GaAs substrates. They were fabricated with selective oxidation and demonstrated room temperature CW operation for the first time. This work is supported by the US DOE under contract No. DE-AC04-94AL85000.
Growth of Direct Bandgap GaInP/GaP Strained Quantum Wells: Jong-Wong Lee, Alfred Schremer, Dan Fekete, and Joseph Ballantyne, Cornell University, Ithaca, NY 14853
GaInP has a direct bandgap for In concentrations higher than approximately 30%. By growing layers thinner than the critical layer thickness, defect-free, pseudomorphic, direct bandgap GaInP quantum wells can be grown on GaP. We have grown a series of pseudomorphic GaInPlGaP quantum wells bv OMVPE, and we have studied light emission from the quantum wells. A study of photoluminescence from the quantum wells reveals that GaInP is ordered and that ordering is beneficial to forming type-I quantum wells. We present dependence of quantum emission characteristics on various growth parameters such as quantum well composition, quantum well thickness, growth temperature, and growth rate.
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