Simulation investigation of tensile strained GeSn fin photodetector with Si3N4 liner stressor for extension of absorption wavelength

In this paper, we design a biaxial tensile strained GeSn photodetector with fin structure wrapped in Si3N4 liner stressor. A large biaxial tensile strain is induced in GeSn fins by the expansion of Si3N4 liner stressor. The distribution of tensile strain in GeSn fins was calculated by a finite element simulation. It is observed that magnitude of the strain increases with the reduction of fin thickness T-fin. Under the biaxial tensile strain, the direct band gap E-GT of GeSn fin photodetector is significantly reduced by lowering G conduction valley in energy and lifting of degeneracy of valence bands. As the 30 nm Si3N4 liner stressor expanses by 1%, a E-G,E-T reduction of similar to 0.14 eV is achieved in Ge0.92Sn0.08 fins with a T-fin of 100 nm. The cut- off wavelengths of strained Ge0.96Sn0.04, Ge0.92Sn0.08 and Ge0.90Sn0.10 fin photodetectors with a Tfin of 100 nm are extended to 2.4, 3.3, and 4 mu m, respectively. GeSn fin photodetector integrated with Si3N4 liner stressor provides an effective technique for extending the absorption edge of GeSn with Sn composition less than 10% to mid- infrared wavelength. (C) 2015 Optical Society of America