Noise analysis of optimized Ge/Ge1-xSnx/Ge p-n-p heterojunction phototransistors for long-wavelength optical receivers

Present literature investigates noise analysis and optimal design for Ge/Ge1-xSnx/Ge based p-n-p heterojunction phototransistors (HPT) for long-wavelength optical receivers. We calculate gain, noise powers, signal-to-noise ratio, absorption coefficient and optical responsivity of proposed GeSn-based HPT and investigate their dependence on various structural parameters to optimize the design. The proposed HPT incorporates Ge1-xSnx alloy in the base layer as the active layer, allow to extend the photo detection range from near infrared to mid-infrared to achieve a wide range of detection. The results show that the signal-to-noise ratio (SNR) is strongly dependent on the operating frequency and the introduction of Sn in the base layer can improve the signal-to-noise ratio in the high-frequency region. The calculated results also show that even in the presence of small defects and misfit dislocations at the heterointerfaces, high SNR is still achievable for the proposed structure.