Highly responsive broadband Si-based MoS₂ phototransistor on high-k dielectric

The demand for photodetectors and image sensors has grown exponentially in the past decade in biomedical, security surveillance, robotics, automotive, quality control, image recognition, and military applications, due to their superior quality, broadband detection, lower noise, and economic viability. Here, we report a MoS₂ channel-based phototransistor over an HfO₂/n-Si substrate isolated by an hBN layer. The high photoresponse is achieved through the integration of the photoconduction, photogating, and mobility enhancement process by utilizing excellent features of MoS₂, HfO₂/Si, and hBN. The capacitive coupling of the photogenerated carriers by high-k dielectric HfO₂ leads to modulation of MoS₂ Fermi level due to electrostatic doping. Furthermore, the MoS₂ also contributes to the photogeneration of carriers due to its semiconducting nature, leading to additional photocurrent. Ultimately, the combination of photogating, photoconduction, and swift carrier extraction with remarkable mobility of 11.65 cm² · V⁻¹ · s⁻¹ results in high responsivity, external quantum efficiency, and detectivity of 4.5 × 10⁸ A · W⁻¹, 0.72 × 10⁶, and 6.20 × 10¹⁶ Jones at 266 nm illumination, respectively. The device also demonstrates broadband photoresponse from 266–1000 nm wavelengths. The high responsivity distinguishes the potential of our device for the future of optoelectronics and broadband image sensing applications.