Tensile-Strained Mid-Infrared GeSn Detectors Wrapped in Si <sub>3</sub>N <sub>4</sub> Liner Stressor: Theoretical Investigation of Impact of Device Architectures

Abstract

In this paper, we comparatively studied the energy band diagram and the cutoff wavelength characteristics of germanium-tin (GeSn) fin and pillar array detectors wrapped in a Si 3 N 4 liner stressor to unveil the impacts of tensile strain and device architecture in the absorption spectra of the devices. A large tensile strain is introduced into GeSn devices by the expansion of the Si 3 N 4 liner stressor. Compared to the fin detector, a larger tensile volume strain is demonstrated in the GeSn pillar architecture. With the tensile strain induced by the Si 3 N 4 liner stressor, the direct bandgap E G,Γ of GeSn is obviously shrinked by lowering the energy of the Γ conduction band valley, which results in a significant extension of absorption edge in the GeSn detectors. As the Si 3 N 4 liner stressor releases internal stress and expands, the absorption edge of the tensile-strained Ge 0.90 Sn 0.10 pillar array detector with the length of side of pillar L pillar of 100 nm is extended to 4.35 μm. With further improvement, the tensile-strained GeSn pillar architecture with the Si 3 N 4 liner stressor will be competitive for the application in 2-5-μm mid-infrared spectra.