Design Optimization of an MoS₂ Based Homojunction and Heterojunction Phototransistor

Two-dimensional transition metal dichalcogenides (TMD)-based photodetectors have demonstrated potential for next generation optoelectronics technology due to their high sensitivity, but at the expense of high bias voltage, not suitable for practical large scale device applications. Here we report molybde-num disulfide <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{MoS}_{2})$</tex> based ultrasensitive pho-totransistor with a vertical p-n homojunction as a sensitizing scheme. The simulated structure produces a photo-responsivity of around <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5 \times 10^{4}\text{AW}^{-1}$</tex>, specific detectivity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.089 \times 10^{14}$</tex> Jones at 1.5 V gate bias and 1V drain bias. The responsivity and specific detectivity are further enhanced by replacing <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{n}-\text{MoS}_{2}$</tex> channel by n-silicon layer, thereby creating <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{p}-\text{MoS}_2 / \mathbf{n}$</tex>-Si heterojunction.