NUS Enterprise

High Sensitivity Graphene-based Photodetector

Technology #10133n

High Sensitivity Graphene-based Photodetector

Prof. Chen Wei, Dr. Chen Zhenyu, Prof Andrew Wee Thye Sen, Dr. Xie Lanfei, Dr. Wang Xiao, Dr. Sun Jiatao, Dr. Ariando

Department of Chemistry

Department of Physics

Industry Problem

Graphene is an attractive material for various applications such as Infra Red (IR) detector, field effect transistor (FET) channel and p-n junction diode rectifier. Graphene doping is necessary to further improve the material conductivity. However, the lack of effective doping methods is a challenge for graphene device development. Conventional doping method via the bombardment of graphene with energetic ions (dopants) followed by thermal annealing can easily destroy the graphene lattice and produce large amounts of defects, thus degrading the device’s performance.

Solution

Prof. Chen Wei’s group from the Department of Chemistry has developed a technique to effectively dope graphene by providing a layer of NUS oxide film on the graphene layer, forming a hole accumulation layer on the graphene. The hole accumulation layer has an areal density of holes of ~ 1013 cm-2. Fig. 3 shows transfer characteristics (gate voltage dependent conductivity) evolution with increasing NUS oxide thickness up to 0.1nm. Shift in Dirac point (the minimum of transfer curve) to higher positive voltages with increasing NUS oxide thickness indicate p-type doping effect of NUS oxide on graphene. In-situ graphene FET measurements demonstrates NUS Oxide deposition increases graphene conductivity (7X) while preserving mobility (Fig. 4). In addition, Graphene (Gr) /Si Schottky junction photodetectors have been fabricated (Fig. 5). NUS Oxide film increases fabricated Gr/Si photodetector sensitivity by up to 4 times (Figs 6(a) & (b)). NUS has filed for patent protection for this invention.

Keywords: photodetector, high sensitivity, graphene, hole doping, oxide

Fig. 1: Fabricated graphene field effect transistors (FET). Inset: the magnified conduction channel.

Fig. 2: Schematic illustration of graphene FET layout with in situ deposition of NUS Oxide thin film.

Fig. 3: Shift in Dirac point (the minimum of transfer curve) to higher positive voltages with increasing NUS oxide thickness indicate p-type doping effect of NUS oxide on graphene.

Fig. 4: NUS Oxide deposition increases graphene conductivity by almost 7 times, slight decrease due to air exposure.

Fig. 5: Schematic of fabricated Graphene (Gr) /Si Schottky junction photodetector. Both NUS Oxide modified and pristine graphene devices are fabricated. 

 Fig. 6: NUS Oxide film increases the Gr/Si photodetector sensitivity by up to 4 times, as shown by the photocurrent responsivity (Rl) and External Quantum Efficiency (EQE). 

Value Proposition

•  Potentially scalable: NUS oxide film may be deposited on graphene layer by conventional methods such as vacuum thermal evaporation.

•  Chemically stable: NUS oxide film has excellent thermal and chemical stability in air and solution.

•  Non-destructive: Effectively dopes graphene while maintaining graphene lattice integrity.

•  Doping technique results in 4X increase in photodetector sensitivity as compared to pristine graphene.

Other Potential Application

•  Semiconductor production

•  Flexible electronics

•  Sensors

For more information, contact:

NUS Industry Liaison Office

Case Manager: Tan Yan Ny

  :+65 6516 7175/ +65 66012812

  : iloquery@nus.edu.sg/ tan.yan.ny@nus.edu.sg

Principal Investigator: Prof Chen Wei

chmcw@nus.edu.sg

Acknowledgement

This research is supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Competitive Research Program

(CRP Award No. NRF-CRP 1-2007 (NUS grant number R-143-000-360-281)).

Ref : ID10133N