Investigation of GaNAsSb/GaAs and GaInNAsSb/GaNAs/GaAs Band Offsets
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Investigation of GaNAsSb/GaAs and GaInNAsSb/GaNAs/GaAs Band Offsets Homan B. Yuen1, Robert Kudrawiec2, K. Ryczko2, S.R. Bank1, M.A. Wistey1, H.P. Bae1, J. Misiewicz2, and J.S. Harris Jr.1 1) Solid State and Photonics Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California 94305-4075 2) Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland Email: [email protected]
ABSTRACT Heterojunction band offsets of GaNAsSb/GaAs, GaInNAsSb/GaAs, and GaInNAsSb/GaNAs/GaAs quantum well (QW) structures were measured by photoreflectance (PR) spectroscopy. These samples were grown by solid-source molecular beam epitaxy using a radio-frequency nitrogen plasma source. PR spectra were collected from the QW structures and the energy transitions were obtained. The experimental data of the QW energy transitions were analyzed by theoretical calculations. Using predetermined values such as QW thickness and composition, unknown factors such as the heterojunction band offsets were able to be determined. For the GaN0.02As0.87Sb0.11/GaAs structure, we found that Qc≈0.5. For Ga0.62In0.38N0.026As0.954Sb0.02/GaAs, we found that Qc≈0.8. This value is similar to the antimony free dilute-nitride material GaInNAs since the small amount of antimony does not affect the band offsets. For the technologically important Ga0.61In0.39N0.023As0.957Sb0.02/GaN0.027As0.973/GaAs laser structure, we found that the GaInNAsSb/GaNAs QW had a conduction band offset of 144 meV and a valence band offset of 127 meV. With a greater understanding of the band structure, more advanced GaInNAsSb laser devices can be obtained.
INTRODUCTION The addition of small amounts of nitrogen into InGaAs has allowed for growth of dilutenitride materials which have much longer emission wavelengths than previously attainable on GaAs.1 GaInNAs has enabled the development of lasers at the important fiber communication wavelength of 1.3 µm.2,3,4 The InGaAsP/InP material system is currently utilized for laser devices operating at 1.3 and 1.55 µm5, the other important communication wavelength, but has several disadvantages compared to the GaAs-based GaInNAs system. GaAs substrates are much cheaper than InP substrates making the economies of scale favorable towards GaAs-based devices. InGaAsP lasers must use a complex system of InP and InGaAsP (of a different composition) for the distributed Bragg reflectors. The refractive index contrast is low and thus requires a large (~60) number of mirror pairs to obtain a high reflectivity coefficient. For GaInNAs, the mature and well-developed AlAs/GaAs system is used. Refractive index contrast
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is high and fewer mirrors pairs (~30) are required, enhancing heat removal from the active regions of the lasers. Oxide-confinement techniques can also be employed to further reduce power requirements and enhance performance characteristics. The InGaAsP/InP system also suffers from a disadvantageous band lineup. 40% of the band offset is found in the conduct
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