Monday, August 5, 2013

1308.0363 (Priyamvada Jadaun et al.)

Electronic and optical properties of GaSb:N from first principles    [PDF]

Priyamvada Jadaun, Hari P. Nair, Vincenzo Lordi, Seth R. Bank, Sanjay K. Banerjee
GaSb:N displays promise towards realization of optoelectronic devices accessing the mid-infrared wavelength regime. Theory and experimental results on its electronic and optical properties are however few. To address this, we present a first principles, density functional theory study using the hybrid HSE06 exchange-correlation functional of GaSb doped with 1.6$%$ nitrogen. To study dilute-nitrides with small band gaps, the local density approximation (LDA) is insufficient and more accurate techniques such as HSE06 are needed. We conduct a comparative study on GaAs:N, also with 1.6$%$ nitrogen mole fraction, and find that GaSb:N has a smaller band gap and displays more band gap bowing than GaAs:N. In addition we examine the orbital character of the bands, finding the lowest conduction band to be quasi-delocalized, with a large N-$3s$ contribution. At high concentrations, the N atoms interact via the host matrix, forming a dispersive band of their own which governs optoelectronic properties and dominates band gap bowing. While this band drives the optical and electronic properties of GaSb:N, its physics is not captured by traditional models for dilute-nitrides. We thus propose that a complete theory of dilute-nitrides should incorporate orbital character examination, especially at high N concentrations. From our calculations, we also find that GaSb:N has a weaker optical matrix element than GaAs:N, though it could be a promising material for optoelectronic applications with the removal of N related clusters and defects.
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