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

Abstract

Degenerately doped (>1019 cm−3) n-type InxGa1−xAs (x∼0.67) and InPyAs1−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 (λp∼5 μm) in comparison to InGaAs films (λp∼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.