Speaker
Description
Investigating the fundamental aspects of photophysics is essential for developing a wide range of optoelectronic devices and systems. However, understanding photocarrier dynamics in two-dimensional materials has been challenging due to significant exciton binding energy and the absence of an effective system for exciton manipulation. In our study, we introduce a WSe2 phototransistor with an asymmetrical split-gate design, termed the asymmetry field-effect phototransistor (AFEPT). This design effectively alters the electric field distribution across the channel, offering a reliable framework for exploring the photocarrier behavior in the intrinsic WSe2 layer. Through controlling electric field, we were able to observe the spatial development of photocurrent across the WSe2 channel. Our findings include the identification of the physical mechanisms behind the unique photocurrent response, and we pinpointed the exciton binding energy at room temperature to be 230 meV using our device.
The demand for polarization-sensitive photodetection is growing, driven by its potential applications in 3D imaging, quantum optics, and secure communication. Traditional photodetectors, typically made from silicon or III-V InGaAs semiconductors, struggle to detect polarized light without extra optical elements. We present a novel, self-powered photodetector sensitive to linear-polarized near-infrared (NIR) light, built using a two-dimensional WSe2/ReSe2 van der Waals heterostructure. This heterojunction photodiode, with its semi-vertical structure, demonstrates exceptional capabilities, including a ideality factor of 1.67, a wide spectral response range (405–980 nm) with a pronounced photovoltaic effect, excellent linearity with a dynamic range exceeding 100 dB, and fast switching speeds with a cutoff frequency reaching 100 kHz. The device's ability to detect polarized excitonic transitions at the ReSe2 band edge results in a notable linear-polarization-dependent photocurrent at 980 nm NIR. This sensitivity to linear polarization is durable, remaining consistent even after over five months of air exposure. Additionally, utilizing the photodiode's selective NIR (980 nm) linear polarization detection capability, we achieved digital incoherent holographic 3D imaging, showcasing its potential for advanced optoelectronic applications.
