Properties of GaAsSb QW Heterostructures Having Various Barrier Materials Grown by Metalorganic Chemical Vapor Depositio
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Properties of GaAsSb QW Heterostructures Having Various Barrier Materials Grown by Metalorganic Chemical Vapor Deposition Min Soo Noh1, Jae Hyun Ryou1, Ying-Lan Chang2, Robert Weissman3, and Russell D. Dupuis1 1 The University of Texas at Austin, Microelectronics Research Center, 10100 Burnet Road, Bldg. 160, Austin TX 78758 2 Agilent Laboratories, Agilent Technologies Inc., 3500 Deer Creek Road, Palo Alto CA 94304 3 Agilent Technologies Inc., 370 Trimble Road, San Jose CA 95131 ABSTRACT Pseudomorphic GaAs1-xSbx quantum-well (QW) structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD) have been studied with various barrier materials to investigate the energy band lineup. To determine the band lineup of these structures, we have performed low-temperature current-dependent cathodoluminescence (LT-CL) measurements at 10K. For the structure with GaAs barriers, the data show strong evidence of Type-II staggered band lineup, which means that holes are confined in the valence band heavy-hole level of the GaAs1-xSbx quantum well and electrons are confined in the conduction band of the GaAs barrier. For the InGaP barriers, however, we observed only one peak that is related to transitions of a Type-I band lineup. From the LT-CL results, we find that the valence-band discontinuity ratio (Qv) between the GaAs0.73Sb0.27 double quantum wells (DQWs) and the GaAs barriers is ~1.20. Furthermore, to improve the carrier confinement, we propose that InGaP barriers provide a Type-I band lineup with the GaAsSb QW. INTRODUCTION Lasers emitting at a wavelength of λ~1.3µm are one of the most important optoelectronic devices because of application to high-bit-rate optical fiber communication systems. Recently, Vertical Cavity Surface Emitting Lasers (VCSELs) operating at a wavelength of ~1.3µm and grown on GaAs substrates have been attracting great interest for high-performance, low-cost communication system applications. GaAsSb materials have been studied for this application [13]. Strained GaAsSb QW heterostructures grown on GaAs substrates can be good candidates for this purpose in spite of the large miscibility gap expected for typical growth conditions, a high strain between GaAs and GaSb (~7.8%), and the expected Type-II band lineup of the GaAsSb/GaAs heterojunction [4-6]. In order to improve the electrical confinement, which gives better device performance, particularly at higher temperatures, a Type-I band lineup is preferable to that of a Type-II alignment. Due to the high strain of GaAsSb layers grown on GaAs substrates, it is hard to grow a thick QW or multiple quantum-wells (MQWs) active layer, which gives higher optical gain. So strain compensation is also needed for high Sb composition layers. Of importance is the band lineup between the quantum-well and the barrier material. In this work, we employ new large bandgap InGaP barrier material to achieve Type-I band lineup with GaAsSb QWs and strain compensation and report the evidence of Type-I emission. We verified Type-I band lineup in struc
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