Dual Mode Photocurrent Generation of Graphene-Oxide Semiconductor Junction

Abstract

The need for low-cost and highly versatile photosensing devices keeps increasing. In this work, we present a heterojunction device based on wafer-scale graphene grown by chemical vapor deposition (CVD) and sputtered InGaZnO (IGZO) semiconductor for dual mode photocurrent collection. The photocurrent can be collected either from the lateral gold/graphene/gold configuration or from the vertical graphene/IGZO/nickel heterojunction configuration with no external bias. Incident-energy-dependent photocurrent scanning microscopy shows that the dominant photocarriers are formed at the edge of the gold electrode through photo-thermoelectric hot hole generation in the lateral configuration. Vertical mode renders unidirectional current flow by photoexcited electrons in the IGZO and the subsequent relaxation and diffusion due to Fowler-Nordheim potential. © 2015 The Electrochemical Society. [DOI: 10.1149/2.0071512jss] All rights reserved.Manuscript submitted July 7, 2015; revised manuscript received September 9, 2015. Published September 22, 2015 Graphene is a two dimensional carbon-chained material that has been extensively studied for promising photonic and optoelectronic applications.1-3 Zero bandgap and a fast carrier relaxation process in intrinsic graphene facilitate ultra-broadband and ultrafast light detectors. [4][5][6][7] Under light illumination, graphene with lateral contact electrodes generates photocurrent through a photovoltaic, bolometric, or photo-thermoelectric mechanisms depending on bias and gating conditions. [8][9][10][11][12][13][14][15] Recently, photodetectors based on graphene heterojunctions have been extensively highlighted. Currently, Schottky-barrier-type vertical heterojunctions composed of graphene/silicon, [16][17][18][19][20] reduced-graphene-oxide (RGO)/silicon, 21 and RGO/silicon nanowire 22 have been successfully demonstrated. Unlike lateral photocurrent collection, the vertical junctions take advantage of an asymmetric barrier potential to efficiently separate photoexcited electrons and holes, which might pave the way for light detection with large active areas without the need for external source-drain bias.Here, we demonstrate a heterojunction device capable of dual mode photocurrent collection under zero source-drain bias based on a graphene grown by chemical vapor deposition (CVD) and amorphousphase indium gallium zinc oxide (IGZO). Here, dual mode means that the photocurrent can flow either from a lateral pair of the electrodes or from a vertical pair of electrodes. Versatile photodetection schemes allow to broaden the range of selection for applications such as photoenergy harvesting, phototransistor, and photoconductive detector. 1,2,14 Unlike silicon, IGZO semiconductors can be grown on glass substrates at low temperatures, typically below 200• C so that large area device fabrication is possible. IGZO has been widely used for image sensors, flat-panel displays, and thin film transistors. [23][24][25] The typical mobility of the IGZO film is about 10-60 cm 2 /Vs. 23,25,26 Interes...

Optical and Magneto‐Tunable Electrical Transport Across La0.7Sr0.3MnO3, Zn0.3Ni0.7Fe2O4/CuPc Hybrid Interfaces

“…Similar kind of hole transport may exist at ZNFO/CuPc interface as band energy difference (ZNFO) ≈ HOMO (CuPc) is also expected to be smaller (upper inset of Figure 4) than (ZNFO) ≈ LUMO(CuPc) at equilibrium. [ 21–24 ] However, the band energy difference (LSMO) ≈ HOMO (CuPc) (0.4 eV) is expected to be larger (upper inset of Figure 4) than (ZNFO) ≈ HOMO(CuPc) (<0.4 eV), which may have resulted in enhanced I–V curve nonlinearity for LSMO device as compared to ZNFO device. [ 21–25 ]…”

“…[ 21–24 ] However, the band energy difference (LSMO) ≈ HOMO (CuPc) (0.4 eV) is expected to be larger (upper inset of Figure 4) than (ZNFO) ≈ HOMO(CuPc) (<0.4 eV), which may have resulted in enhanced I–V curve nonlinearity for LSMO device as compared to ZNFO device. [ 21–25 ]…”

“…[21][22][23][24] However, the band energy difference E F (LSMO) % HOMO (CuPc) (0.4 eV) is expected to be larger (upper inset of Figure 4) than E F (ZNFO) % HOMO(CuPc) (<0.4 eV), which may have resulted in enhanced I-V curve nonlinearity for LSMO device as compared to ZNFO device. [21][22][23][24][25] The carrier injection into HOMO or LUMO levels of CuPc can be mediated by phonons at RT. [26] In order to substantiate the effect of phonon-assisted transport, we have adopted a theoretical model proposed by Kiveris and Pipinys, [27,28] which considers field emission from electrode-organic interface defect states to the HOMO level of organic semiconductor (OSC) along with multiphonon activation of electrons at CuPc organic transport layer of the devices.…”