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▲ [16a-C301-1] Sn Content Dependent Absorption in GeSn Quantum Well Layer for Infrared Sensing
Keywords:Quantum well, Absorption, Sensing
Recently there has been a great deal of interest among researchers on the design and analysis of photosensitive devices based on Tin (Sn) incorporated Group-IV alloys. Alloying Ge with Sn can effectively reduce the direct-bandgap of Ge more than its indirect bandgap and, hence, a direct-bandgap GeSn alloy can be realized. This paper focuses on the potential of Tin doped group-IV alloys specially GeSn. Sn dependent direct-absorption characteristic in strain balanced SiGe/GeSn quantum well(QW) is determined by solving time independent Schrödinger equation. Finite difference method is used to solve the Schrödinger equation for gamma valley, heavy hole(HH) band. The model, considered in our analysis, consists of tensile strained SiGeSn barriers and compressive strained GeSn well which ensure the strain balanced condition for quantum well. The strain balanced condition minimizes the total strain energy to reduce the strain-misfit dislocation density. A 76 angstrom thick Ge(1-x) Sn(x) layer is sandwiched between two tensile strained Si(0.09)Ge(0.8)Sn(0.11) layers to form a type-I single quantum-well (QW). A fully relaxed GeSn layer is used as a buffer layer. Width of the barrier layers is determined to be 34.6 angstrom by using the strain balanced condition for a cubic based multilayer system . The band alignments are calculated using the model solid theory , and band offsets are calculated considering bowing parameter. Schrödinger equation for QW considering the strain effect and effective-mass is used in our analysis. After obtatining Eigen state energies in conduction band and valence band (HH), absorption coefficient for HH-conduction band transition is determined. The result shows that there is a significant absorption observed in the range of 3-5 micron for different Sn cocnentration (0.15-0.18 ). So, this structure is viable to be used as a low cost monolithic infrared sensor.