Influence of Growth Parameters and Annealing on Properties of MBE Grown GaAsSbN SQWs
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Influence of Growth Parameters and Annealing on Properties of MBE Grown GaAsSbN SQWs Liangjin Wu, Shanthi Iyer, Kalyan Nunna, Sudhakar Bharatan, Jia Li, and Ward J. Collis Department of Electrical and Computer Engineering, North Carolina A&T State University, Greensboro, NC 27411 ABSTRACT In this paper we report the growth of GaAsSbN/GaAs single quantum well (SQW) heterostructures by molecular beam epitaxy (MBE) and their properties. A systematic study has been carried out to determine the effect of growth conditions, such as the source shutter opening sequence and substrate temperature, on the structural and optical properties of the layers. The substrate temperatures in the range of 450-470 ˚C were found to be optimal. Simultaneous opening of the source shutters (SS) resulted in N incorporation almost independent of substrate temperature and Sb incorporation higher at lower substrate temperatures. The effects of ex-situ annealing in nitrogen ambient and in-situ annealing under As overpressure on the optical properties of the layers have also been investigated. A significant increase in photoluminescence (PL) intensity with reduced full width at half maxima (FWHM) in conjunction with a blue shift in the emission energy was observed on annealing the samples. In in-situ annealed samples, the PL line shapes were more symmetric and the temperature dependence of the PL peak energy indicated significant decrease in the exciton localization energy as exhibited by a less pronounced “S-shaped curve”. The “inverted S-shaped curve” observed in the temperature dependence of PL FWHM is also discussed. 1.61 µm emission with FWHM of 25 meV at 20K has been obtained in in-situ annealed GaAsSbN/GaAs SQW grown at 470 ˚C by SS.
I. INTRODUCTION The dilute nitride InGaAsN/GaAs heterostrutures have received special attention due to their applications in the 1.3 µm range for laser based radar and optical communication applications[1-5]. However, to extend the wavelength close to 1.55 µm in this material system requires 5% N [6], which exceeds the solubility limit and causes significant degradation in emission efficiency. Other alternative material systems that are currently being investigated in the literature are InGaAsSbN [5,7,8] and GaAsSbN [9-15]. In GaAsSbN/GaAs QWs the 1.55 µm wavelength can be reached at a much lower concentration of ~1% N [14]. In general, Sb incorporation in the layer was found to be sensitive to the growth temperature and the presence of Sb flux prior to the layer growth in the antimonide systems [16,17]. Also, the presence of Sb affects N incorporation in the antimonide based dilute nitride epilayers [10,11]. These observations suggest that the growth parameters and procedures play an
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important role in the incorporation of Sb and N and the quality of the interface. Thermal annealing of the dilute nitride alloy system, in general, has been known [1,2] to improve the photoluminescence (PL) emission efficiency at the expense of the blue shift. Also, in these systems temperature dependence of
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