Moss-Burstein and plasma reflection characteristics of heavily doped n-type In_xGa_1-xAs and InP_xAs_1-y

Degenerately doped (> 10¹⁹cm^-3) n-type In_xGa_1-xAs (x∼0.67) and InP_yAs_1-y (y∼0.65) possess a number of intriguing electrical and optical properties relevant to electro-optic devices and thermophotovoltaic devices in particular. Due to the low electron effective mass of these materials (m*<0.2) and the demonstrated ability to incorporate n-type dopants into the high 10¹⁹ cm^-3 range, both the Moss-Burstein band gap shift and plasma reflection characteristics are particularly dramatic. For InGaAs films with a nominal undoped band gap of 0.6 eV and N = 5× 10¹⁹ cm^-3, the fundamental absorption edge increased to 1.27 eV. InPAs films exhibit a shorter plasma wavelength (λ_p∼5 μm) in comparison to InGaAs films (λ_p∼6 μm) with similar doping concentrations. The behavior of the plasma wavelength and the fundamental absorption edge are investigated in terms of conduction band nonparabolicity and Γ-L valley separation using detailed band structure measurements and calculations.