Modelling and Simulation of Ge Absorber-based Tunnel Field-Effect Phototransistor at 1550 nm

Abstract

In this article, a semi-analytical model for germanium absorber-based SOI-tunnel field-effect phototransistor at 1550 nm has been proposed. The model works efficiently for a wide range of intensities i.e. 10−2 to 102 µW/µm2 under the application of a very low gate voltage of 0.54 V. Exhaustive simulations using numerical ATLAS 2D device simulation tool with LUMNINOUS optical module have been carried out to propose the merit of tunnel field-effect transistors (TFETs) over metal oxide semiconductor field effect transistors (MOSFETs) for optical applications. The proposed TFET design provides a way to assist the ultrasensitive optical interconnects at a very low gate bias of 0.54 V with a maximum sensitivity of 1.5 × 107, responsivity of 270 mA/W, and detectivity of 3.5 × 1012 Jones at low power density of 0.01 µW/µm2. The TFET performance has further been improved by introducing a heavily doped pocket in between source and channel, which serves as a potential alternative for photodetector applications. The proposed pocket-doped TFET design offers significant improvements in device optical response with optimized sensitivity of 4.1 × 107, a responsivity of 772 mA/W, and a detectivity of 9.9 × 1012 Jones at an optical intensity of 0.01 µW/µm2, gate bias of 0.45 V, and drain voltage of 0.6 V. Transient analysis has been carried out to optimize the response time of the phototransistor for both Ge-gated conventional TFET and pocket-doped architecture and the fall time of ∼0.22 ms has been achieved.