Quantum Hall Dual-Band Infrared Photodetector

Chiu-Chun Tang, K. Ikushima, D. C. Ling, C. C. Chi, and Jeng-Chung Chen

Phys. Rev. Applied 8, 064001 – Published 1 December 2017

Abstract

We have developed a hybrid quantum Hall midinfrared (QHMIR)–quantum Hall far-infrared (QHFIR) photodetector by the use of graphene- $GaAs / (Al, Ga) As$ –layered composite material. Both MIR and FIR photoresistance are observed in a single chip by utilizing cyclotron resonance in the quantum Hall regimes of graphene and two-dimensional electron gas (2DEG) in $GaAs / (Al, Ga) As$ heterostructure, respectively. By cooperatively operating 2DEG as a back-gate electrode to change the carrier density of graphene or graphene as a top-gate electrode to modulate the carrier density of 2DEG with an applied gate voltage less than 1 V and applying the magnetic field to tune cyclotron resonance, we achieve a wide frequency selectivity, covering $640 - 790 {cm}^{- 1}$ for the graphene-QHMIR detector and $24 - 89 {cm}^{- 1}$ for the 2DEG-QHFIR detector. Moreover, our design integrates a log-periodic antenna with the detector to minimize the device size, while preserving high sensitivity. Our results pave the way for implementing a highly tunable MIR-to-FIR photodetector and a dual-band (MIR-FIR) imaging array.

Received 25 May 2017

DOI:https://doi.org/10.1103/PhysRevApplied.8.064001

Physics Subject Headings (PhySH)

Landau levels Optoelectronics Photoconductivity Quantum Hall effect

Graphene III-V semiconductors Solid-state detectors

Infrared techniques

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Chiu-Chun Tang¹, K. Ikushima², D. C. Ling³, C. C. Chi¹, and Jeng-Chung Chen¹

¹Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
²Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
³Department of Physics, Tamkang University, Tamsui District, New Taipei City 25137, Taiwan

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Vol. 8, Iss. 6 — December 2017

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Images

Figure 1
(a) Schematic configuration of a graphene–GaAs-2DEG capacitively coupled bilayer system. (b) Plot of the Landau-level (LL) energy $E_{N}^{gr}$ of graphene and $E_{n}^{2 D}$ of GaAs-2DEG as a function of the magnetic field $B$ for Landau index $N = 0$ , $\pm 1$ , $\pm 2$ and $n = 0$ , 1, 2, respectively. Schematic diagram of the LL density of states (DOSs) of (c) GaAs-2DEG and (d) graphene. Extended and localized states are represented by bright and dark colors, respectively. Energy levels are broadening in the presence of disorder. When the photon energy matches LL energy spacing, electron-hole pairs are generated, giving rise to a measurable photoresponse.
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Figure 2
(a) Schematic layout (in scale with the real device) of the quantum Hall dual-band photodetector by use of graphene- $GaAs / (Al, Ga) As$ heterostructure composite material. The hybrid device consists of GaAs-2DEG, graphene, metal contacts for the gate and source-drain electrodes, log-periodic antenna, and ionic liquid. (b) Enlarged view of the photosensitive area. (c) Four-terminal longitudinal resistance of the graphene $R_{x x}^{gr}$ as a function of the voltage $V_{g}^{lq}$ applied to the ionic-liquid gate at room temperature ( $T = 300 K$ ). (d) $R_{x x}^{gr}$ as a function of the voltage $V_{g}^{2 D}$ applied to the 2DEG gate at $T = 2$ , 10, and 20 K with $V_{g}^{lq} = 0 V$ . The black dashed line denotes the charge neutral point (CNP) of graphene at $V_{CNP}^{2 D} = 0.46 V$ . (e) Current $I^{2 D}$ through 2DEG versus the voltage $V_{g}^{gr}$ applied to the graphene gate at $T = 2 K$ and $V_{g}^{lq} = 0 V$ . The insets in (c) to (e) show the measurement circuitries.
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Figure 3
(a) The magnetoresistance $R_{x x}^{2 D}$ (dashed line) and photoresponse $Δ R_{sig}^{2 D}$ (solid line) of the QHFIR detector as a function of $B$ at 1.5 K. The upper-left schematics shows the measurement setup. The shaded areas marked with integers correspond to the QHS regimes of the 2DEG with its integer filling factors $ν^{2 D}$ . $Δ R_{sig}^{2 D}$ at (b) $ν^{2 D} \sim 4.5$ and (c) $ν^{2 D} \sim 2.7$ as a function $B$ at various $V_{g}^{gr}$ from 0.4 V to $- 0.1 V$ in a step of $Δ V_{g}^{gr} = - 0.1 V$ . The corresponding cyclotron frequency is indicated in the upper scale.
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Figure 4
Device characterization and performance for QHMIR detector (a) Graphene magnetoresistance $R_{x x}^{gr}$ versus $V_{g}^{2 D} − V_{CNP}^{2 D}$ for various $B$ at 2 K, measured with $I^{gr} = 0.5 μ A$ . The hollow squares and solid triangles indicate the evolutions of the peak and the valley of $R_{x x}^{gr}$ with $B$ , respectively. These features can be resolved as $B > 5 T$ . (b) The $B$ dependence of $n^{gr}$ extracted from the data of the hollow squares and solid triangles in (a). For comparison, the fitted solid lines indicate $n^{gr}$ associated with filling factor $ν^{gr} (= h n^{gr} / e B) = - 2$ and $- 4$ . (c) The photoresponse $Δ R_{sig}^{gr}$ as a function of $V_{g}^{2 D} − V_{CNP}^{2 D}$ for various $B$ at 2 K. The traces have been shifted for clarity. When the optical shutter is closed, the key features on $Δ R_{sig}^{gr}$ disappear, as shown in the green trace at $B = 8 T$ . This dark photoresponse is presented by the green dashed lines for the rest traces. The arrows indicate the positions of $ν^{gr} = - 4$ and zero (at $V_{g}^{2 D} = V_{CNP}^{2 D}$ ). The shaded area covered $ν^{gr} \sim - 4$ indicates the regime where CR absorption of graphene is justified (see Ref. [25] and main text for details).
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Figure 5
The $Δ R_{sig}^{2 D}$ at $ν^{2 D} = 6.3$ , 4.5, and 2.7 and $Δ R_{sig}^{gr}$ at $ν^{gr} = - 3.8$ and $- 3.5$ as a function of cyclotron frequency.
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