High detectivity visible-blind SiF4 grown epitaxial graphene/SiC Schottky contact bipolar phototransistor

Chava, Venkata S. N.; Barker, Bobby G.; Balachandran, Anusha; Khan, Asif; Simin, Grigory; Greytak, Andrew B.; Chandrashekhar, M. V. S.

doi:10.1063/1.5009003

Cited by 16 publications

(10 citation statements)

References 37 publications

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“…In this paper, we create spatially and electronically separated QD/EG and QD/SiC junctions to isolate the remaining PbS-QD/SiC interface. This enabled separate examination using localized illumination for scanning photocurrent microscopy (SPCM). , The architecture presented in Figure enabled us to exploit the following phenomenological observations to achieve this: (i) ohmic contacts of graphene to ethanedithiol (EDT)-capped PbS QDs in air, consistent with p-type conduction reported previously, which was also verified in the current work; (ii) a robust and ideal Schottky diode of EG/SiC that is shown in this paper to be completely recoverable by selective chemical removal using hydrofluoric acid; (iii) a 10–15 monolayer (ML) EG film that achieves optical transparency for optoelectronic characterization, while having a thickness greater than 1–2 ML screening length, such that electrostatic screening of the EG/SiC rectifying junction from the ohmic EG/PbS-QD film junction is achieved, precluding any potential barristor action. , This confluence of favorable conditions eliminates uncertainties stemming from the reproducibility of contacts between samples and between successive PbS-QD film depositions.…”

Section: Introductionsupporting

confidence: 78%

“…We have recently explored optoelectronic properties of Schottky diodes and bipolar phototransistors based on the tetrafluorosilane (SiF 4 , TFS) grown contacts of epitaxial graphene (EG) on a SiC substrate to form a graphene/WBG interface. − These devices are sensitive to ultraviolet light based on the bandgap of 4H-SiC. Here, we demonstrate that these devices respond to NIR light as a direct consequence of the rectifying junction formed between the QD film and n-type 4H-SiC.…”

Section: Introductionmentioning

confidence: 94%

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Photovoltaic and Photoconductive Action Due to PbS Quantum Dots on Graphene/SiC Schottky Diodes from NIR to UV

Kelley

Letton

Simin

et al. 2019

ACS Appl. Electron. Mater.

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We demonstrate photovoltaic and photoconductive responses to near-infrared light in devices formed by depositing a film of gel permeation chromatography purified PbS quantum dots (QDs) on top of n-SiC epitaxial layers with natively grown, low-leakage 10–15 monolayer thick epitaxial graphene (EG) Schottky contacts. The QD film layer was removable by selective chemical etching, resetting the EG/SiC Schottky diode: the sub-bandgap response could be restored in subsequent PbS-QD depositions. The EG in these devices simultaneously forms Schottky contacts to SiC and ohmic contacts to PbS-QD, enabling electrical screening and isolation of these interfaces from each other. After PbS-QD deposition, the diodes exhibit photovoltaic and photoconductive responses at photon energies far below the SiC bandgap, extending to the NIR gap of the QD film. Scanning photocurrent microscopy illustrates that this is due to charge transfer from the QD film to the n-type 4H-SiC through a trap-limited, rectifying PbS-QD/SiC heterojunction with ideality n = 2 in parallel with the EG/SiC Schottky diode. The photoconductive gain at this QD/SiC interface could be useful for IR detection in wide-bandgap platforms. Response times as fast as 40 ms are suitable for imaging applications, although careful contact design is required to optimize work-function matching and spreading resistance.

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Section: Introductionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 94%

Photovoltaic and Photoconductive Action Due to PbS Quantum Dots on Graphene/SiC Schottky Diodes from NIR to UV

Kelley

Letton

Simin

et al. 2019

ACS Appl. Electron. Mater.

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“…The detectivity of the PDs, which is indicative of their overall performance, is given as where A (cm 2 ) is the total exposure area of the PD, including the metalized areas (see Figure (a)), B (Hz) is the bandwidth, and NEP (W) is the noise equivalent power of the PD. To determine the NEP of our PD, we first estimated the total noise power which is equal to the sum of the shot noise power P s (Ampere 2 ) and the 1/ f flicker noise power P 1/ f (Ampere 2 ).…”

Section: Results and Discussionmentioning

confidence: 99%

“…Therefore, it can be concluded that the 1/ f flicker noise is dominant in the range of 1 to 100 Hz, while after 100 Hz, the noise spectrum becomes flat. For a bandwidth of B , the total flicker noise current was given as , …”

Section: Results and Discussionmentioning

confidence: 99%

An AlGaN/GaN Dual Channel Triangular Microcantilever Based UV Detector

et al. 2022

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The UV detection capabilities of III-nitride dual channel triangular microcantilevers, consisting of AlGaN/GaN two-dimensional electron gas channels with an intervening GaN layer, were investigated using 265, 315, and 375 nm illumination. High spectral responsivities, up to 2.3 × 10 4 A/W, were observed along with a very low dark current of a few pA, which resulted in a detectivity of 4.99 × 10 8 Jones. A high UV−visible rejection ratio of 10 4 was also measured between the wavelengths of 265 and 450 nm. A simple analysis of the photogenerated carriers indicates that the high responsivity arises out of a trap related high internal gain mechanism, while the low dark current and high photocurrent are caused by the suspended GaN interchannel layer and tapered channel geometry. The unique combination of high responsivity and detectivity, high gain, low dark currents, and high UV−visible rejection ratio can lead to the design of novel high-performance visible blind and solar blind UV photodetectors.

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“…Further, we compared the device performance to those of other UV photodetectors, including graphene/4H-SiC-based photodetectors, [11,14,17,37,[50][51][52] as shown in Table 1. Our devices showed a higher R with a relatively lower working voltage.…”

Section: Resultsmentioning

confidence: 99%

High‐Responsivity Graphene/4H‐SiC Ultraviolet Photodetector Based on a Planar Junction Formed by the Dual Modulation of Electric and Light Fields

Chen

et al. 2020

Advanced Optical Materials

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Ultraviolet (UV) photodetectors have been fabricated on a graphene/4H-SiC wafer. In this device, the electrical doping in the graphene layer, under the gate, is realized by changing the gate voltage while the optical doping in the graphene layer outside the gate region is realized through the photogenerated carrier injection from SiC, by laser excitation at 325 nm. This kind of dual modulation of optical and electric fields ultimately results in the formation of a planar n-p-n or n-n-n junction in the graphene layer. The photoresponse results demonstrate that the planar n-p-n junction is formed at the negative gate voltage, and facilitates negative photoconductivity. The n-n-n junction is formed at the positive gate voltage and facilitates normal photoconductivity. The maximum responsivity, which is attributable to the high photoconductive gain in the planar n-n-n junction, is 254.1A W −1 , at drain-source voltage of −3 V and gate-source voltage of 3 V. Based on these results, the estimated lifetime of the electrons in the graphene channel extends greatly to more than four orders of magnitude longer than that in the isolated graphene. The above results prove that this graphene/4H-SiC combined structure possesses great potential in practical UV-detection applications.

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High detectivity visible-blind SiF4 grown epitaxial graphene/SiC Schottky contact bipolar phototransistor

Cited by 16 publications

References 37 publications

Photovoltaic and Photoconductive Action Due to PbS Quantum Dots on Graphene/SiC Schottky Diodes from NIR to UV

Photovoltaic and Photoconductive Action Due to PbS Quantum Dots on Graphene/SiC Schottky Diodes from NIR to UV

An AlGaN/GaN Dual Channel Triangular Microcantilever Based UV Detector

High‐Responsivity Graphene/4H‐SiC Ultraviolet Photodetector Based on a Planar Junction Formed by the Dual Modulation of Electric and Light Fields

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