Direct band gap InxGa1−xAs/Ge type II strained quantum wells for short-wave infrared p–i–n photodetector

Abstract

We theoretically investigate GaAs/Ge/InGaAs as a quantum wells for the design of short-wave infrared p–i–n photodetectors in which the quantum well Ge/InGaAs is the active region. At room temperature, strained Ge/InxGa1−xAs becomes a direct band gap when In composition x is lower than 2.5% and 5% respectively. We have calculated the electronic band parameters for the heterointerface Ge/InxGa1−xAs. Then, a type-II strain GaAs/Ge/In0.35Ga0.65As/GaAs quantum wells heterostructure optimized in terms of compositions and thicknesses is studied by solving Schrödinger equation as well as the absorption coefficient (>1.5×104cm−1). These computations have been used for the study of p–i–n infrared photodetectors operating at room temperature in the range 1.3–1.55μm. The electron transport in the GaAs/Ge/In0.35Ga0.65As/GaAs multi-quantum wells-based p–i–n structure was analyzed and numerically simulated taking into account tunneling process and thermally activated transfer through the barriers mainly. The temperature dependence of dark current mechanisms and zero-bias resistance area product (R0A) have been analyzed. Extracted from current–voltage characteristics, R0A products above 3.6⋅106Ωcm2 at 77K were calculated, and the quantitative analysis of the J–V curves showed that the dark current density of Ge/In0.35Ga0.65As photodetector is dominated by generation–recombination processes. The suitability of the modeled photodetector is approved by its feasibility of achieving good device performance near room temperature operating at 1.55μm. Quantum efficiency of ∼90% and responsivity ∼0.6A/W, have been achieved.