High-Performance WSe₂ Phototransistors with 2D/2D Ohmic Contacts

Abstract

We report high-performance WSe phototransistors with two-dimensional (2D) contacts formed between degenerately p-doped WSe and undoped WSe channel. A photoresponsivity of ∼600 mA/W with a high external quantum efficiency up to 100% and a fast response time (both rise and decay times) shorter than 8 μs have been achieved concurrently. More importantly, our WSe phototransistor exhibits a high specific detectivity (∼10 Jones) in vacuum, comparable or higher than commercial Si- and InGaAs-based photodetectors. Further studies have shown that the high photoresponsivity and short response time of our WSe phototransistor are mainly attributed to the lack of Schottky-barriers between degenerately p-doped WSe source/drain contacts and undoped WSe channel, which can reduce the RC time constant and carrier transit time of a photodetector. Our experimental results provide an accessible strategy to achieve high-performance WSe phototransistor architectures by improving their electrical transport and photocurrent generation simultaneously, opening up new avenues for engineering future 2D optoelectronic devices.

Various Structures of 2D Transition‐Metal Dichalcogenides and Their Applications

“…The relatively low carrier mobility of general TMDs limits their application in high‐frequency devices; however, InSe has been reported to possess a high carrier mobility exceeding 10 3 cm 2 V −1 s −1 at room temperature . Referring to the photoelectric properties of TMDs, phototransistors based on TMDs (such as SnSe 2 and WSe 2 ) exhibit high photoresponsivity and short response time . MoTe 2 has been utilized in high‐speed waveguide photodetectors in the telecommunication spectral range .…”

“…[44] Referring to the photoelectric properties of TMDs, phototransistors based on TMDs (such as SnSe 2 and WSe 2 ) exhibit high photoresponsivity and short response time. [45][46][47] MoTe 2 has been utilized in highspeed waveguide photodetectors in the telecommunication spectral range. [48] Various TMDs have also been investigated for solar applications.…”

WSe2 Photovoltaic Device Based on Intramolecular p–n Junction

“…An ultrahigh responsivity phototransistor based on MoS 2 channel, has been realized by ferroelectrics . A high‐performance WSe 2 phototransistor with degenerately p‐doped WSe 2 as 2D contact has also been reported . In addition, flexible photoresistors have been realized based on SnSe and SnS, showing great potentials of 2DLMs in wearable devices.…”

Gate‐Tunable Photoresponse Time in Black Phosphorus–MoS2 Heterojunctions

“…It is well‐known that a strong Fermi level pinning effect exists at MoS 2 –metal interfaces, a key limiting factor in achieving high performance 2D devices involving TMDs . Potential workarounds to reducing Schottky barrier effects include chemical doping of MoS 2 with AuCl 3 , adding heavily doped TMDs between MoS 2 and metal contacts to generate extremely narrow depletion regions, and using gated‐graphene contact to achieve negligible Schottky barriers . These approaches may further improve the photoresponse time of BP–MoS 2 heterojunctions.…”