MOCVD Growth and Characterization of GaInNAs/GaAs/InGaAs/GaAs Quantum Well Structures
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MOCVD Growth and Characterization of GaInNAs/GaAs/InGaAs/GaAs Quantum Well Structures Abdel-Rahman A. El-Emawy, Hongjun Cao, Noppadon Nuntawong, Chiyu Liu, and Marek Osin´ski Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, NM 87106-4343, U.S.A. ABSTRACT Effects of MOCVD growth parameters on structural and optical properties of doublequantum-well (DQW) structures containing uncoupled GaInNAs/GaAs and InGaAs/GaAs quantum wells have been investigated. By varying growth temperature, growth rate, V/III ratio, and DMHy flow rates, we have achieved a longer-wavelength emission from a GaInNAs well than from an InGaAs well grown in the same structure. GaInNAs/GaAs multiple-quantum-well structures grown under optimum conditions emitted at 1.25 µm. INTRODUCTION Semiconductor lasers emitting at 1.3 µm and 1.55 µm have been widely used in optical fiber communication systems due to minimum fiber propagation loss at these optical communication windows. Different semiconductor materials have been used to fabricate lasers emitting at these technologically important wavelengths. The most extensively investigated system is InGaAsP/ InP. However, InGaAsP/InP lasers suffer from poor characteristic temperature (T0) due to the small conduction band offset [1]. Therefore, in practical applications these lasers require costly temperature-control systems. Some improvement in electron confinement has been achieved by replacing the InGaAsP active region with AlInGaAs [2]. The value of T0 ≈ 80 K in AlInGaAs/ InP lasers is, however, still significantly lower than that of 980-nm InGaAs/GaAs-based lasers whose T0 is over 150 K. Another possible candidate material for telecommunication spectral windows is the system of InAs quantum dots (QDs) grown on GaAs. Although very encouraging results have been reported, with T0 as high as 232 K [3], the QD technology is still relatively immature and requires significant further development. Yet another material system that is attractive for fiberoptic communication systems is GaInNAs grown on GaAs, first suggested by Kondow et al. [4]. Adding nitrogen to InGaAs was found to decrease the bandgap and the lattice constant. Moreover, GaInNAs alloy can be grown lattice matched to GaAs. Subsequently, a large number of research groups worked on the growth and characterization of this novel material. The results from this extensive work, within a short time, showed that GaInNAs/GaAs system has significant advantages over other material systems. High T0 of 215 K was reported [5], due to the large conduction band offset. Increasing the In content and the number of quantum wells was observed to reduce the threshold current [6]. In contrast, increasing nitrogen content was reported to degrade crystalline quality and to increase the threshold current density [7]. In this paper, we report on growth of GaInNAs/GaAs quantum wells by MOCVD, using dimethylhydrazine (DMHy) as nitrogen precursor. We investigate the dependence of optical and structural properties of GaInNAs/
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