Polarity-Tunable Field Effect Phototransistors
Jintao Fu, Hao Jiang, Changbin Nie, Feiying Sun, Linlong Tang, Yunjie Li, Zhancheng Li, Wen Xiong, Jun Yang, Xin Li, Dahua Zhou, Jun Shen, Shuanglong Feng, Haofei Shi, Paul Mulvaney, Xingzhan Wei
Abstract
Field-effect phototransistors feature gate voltage modulation, allowing dynamic performance control and significant signal amplification. A field-effect phototransistor can be designed to be inherently either unipolar or ambipolar in its response. However, conventionally, once a field-effect phototransistor has been fabricated, its polarity cannot be changed. Herein, a polarity-tunable field-effect phototransistor based on a graphene/ultrathin Al 2 O 3 /Si structure is demonstrated. Light can modulate the gating effect of the device and change the transfer characteristic curve from unipolar to ambipolar. This photoswitching in turn produces a significantly improved photocurrent signal. The introduction of an ultrathin Al 2 O 3 interlayer also enables the phototransistor to achieve a responsivity in excess of 10 5 A/W, a 3 dB bandwidth of 100 kHz, a gain–bandwidth product of 9.14 × 10 10 s –1, and a specific detectivity of 1.91 × 10 13 Jones. This device architecture enables the gain–bandwidth trade-off in current field-effect phototransistors to be overcome, demonstrating the feasibility of simultaneous high-gain and fast-response photodetection.