Moss–Burstein and plasma reflection characteristics of heavily doped n-type InxGa1−xAs and InPyAs1−y

Degenerately doped ${\text{(>10}}^{19} {\mathrm{cm}}^{\mathrm{-3}})$ n-type ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{As}$ $\text{(x∼0.67)}$ and ${\mathrm{InP}}_y{\mathrm{As}}_{\text{1−y}}$ $\text{(y∼0.65)}$ 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 ${\mathrm{(m}}^{*}\text{<0.2)}$ and the demonstrated ability to incorporate n-type dopants into the high ${10}^{19} {\mathrm{cm}}^{\mathrm{-3}}$ 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 ${\text{N=5×10}}^{19} {\mathrm{cm}}^{\mathrm{-3}},$ the fundamental absorption edge increased to 1.27 eV. InPAs films exhibit a shorter plasma wavelength ${\mathrm{(\lambda }}_p\text{∼5\hspace{0.05em}μ}\mathrm{m})$ in comparison to InGaAs films ${\mathrm{(\lambda }}_p\text{∼6\hspace{0.05em}μ}\mathrm{m})$ with similar doping concentrations. The behavior of the plasma wavelength and the fundamental absorption edge are investigated in terms of conduction band nonparabolicity and $\mathrm{\Gamma -L}$ valley separation using detailed band structure measurements and calculations.