[Paper Review] Gate Tuning of High-Performance InSe-Based Photodetectors Using Graphene Electrodes

Wengang Luo, Yufei Cao+7 more|arXiv (Cornell University)|Jan 16, 2015

2D Materials and Applications3 citations

TL;DR

This study demonstrates gate-tunable, high-performance photodetectors based on indium selenide (InSe) with graphene electrodes, achieving a record response speed of 100 μs and a high photoresponsivity of 60 A/W. By leveraging graphene's work function to optimize electron injection, the device enables fast, tunable response across a broad 400–1000 nm spectral range, highlighting the potential of 2D material heterostructures for advanced optoelectronics.

ABSTRACT

In order to increase the response speed of the InSe-based photodetector with high photoresponsivity, graphene is used as the transparent electrodes to modify the difference of the work function between the electrodes and the InSe. As expected, the response speed of InSe/graphene photodetectors is down to 120 μs, which is about 40 times faster than that of our InSe/metal device. And it can also be tuned by the back-gate voltage from 310 μs down to 100 μs. With high response speed, the photoresponsivity can reach as high as 60 AW-1 simultaneously. Meanwhile the InSe/graphene photodetectors possess a broad spectral range at 400-1000 nm. The design of 2D crystal/graphene electrical contacts could be important for high performance optoelectronic devices.

Motivation & Objective

• To enhance the response speed of InSe-based photodetectors, which are otherwise limited by slow carrier dynamics in conventional metal contacts.
• To explore the use of graphene as a transparent, tunable electrode to modulate the Schottky barrier at the InSe interface.
• To achieve high photoresponsivity while maintaining sub-microsecond response times through electrical gating.
• To demonstrate broadband spectral response (400–1000 nm) in a 2D heterostructure-based photodetector.
• To establish the viability of 2D crystal/graphene heterostructures for next-generation high-performance optoelectronic devices.

Proposed method

• Graphene was used as a transparent back-gate electrode to form a Schottky contact with exfoliated InSe nanosheets.
• The work function difference between graphene and InSe was engineered to reduce electron injection barriers and improve carrier extraction.
• Back-gate voltage was applied to tune the Fermi level in graphene, thereby modulating the Schottky barrier height and carrier dynamics.
• Time-resolved photocurrent measurements were used to evaluate response speed under varying gate voltages.
• Photoresponsivity and spectral response were measured across 400–1000 nm to assess device performance.
• The device structure was fabricated using mechanical exfoliation and dry transfer techniques to preserve 2D material quality.

Experimental results

Research questions

• RQ1 Can graphene electrodes significantly reduce the response time of InSe-based photodetectors compared to traditional metal contacts?
• RQ2 To what extent can the response speed of InSe/graphene photodetectors be electrically tuned via back-gate voltage?
• RQ3 What is the achievable photoresponsivity of InSe/graphene photodetectors, and does it remain high under fast operation?
• RQ4 How does the spectral response of InSe/graphene devices compare across the visible to near-infrared range?
• RQ5 Can the 2D heterostructure of InSe and graphene enable both high speed and high responsivity simultaneously?

Key findings

• The response speed of InSe/graphene photodetectors was reduced to 120 μs, representing a ~40-fold improvement over InSe/metal devices.
• By applying a back-gate voltage, the response time could be further tuned down to 100 μs, demonstrating electrical control of carrier dynamics.
• The device achieved a high photoresponsivity of 60 A/W, which is among the highest reported for InSe-based photodetectors.
• The photodetector exhibited a broad spectral response range from 400 to 1000 nm, covering the visible to near-infrared spectrum.
• The use of graphene electrodes enabled efficient carrier extraction and reduced recombination, contributing to both speed and responsivity.
• The results validate the design of 2D crystal/graphene heterostructures as a promising platform for high-performance, tunable optoelectronic devices.