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Hybrid graphene/n-GaAs photodiodes with high specific detectivity and high speed

TIAN Hui-jun LIU Qiao-li YUE Heng HU An-qi GUO Xia

田慧军, 刘巧莉, 岳恒, 胡安琪, 郭霞. 高比探测率和高速石墨烯/n-GaAs复合结构的光电探测器[J]. 中国光学. doi: 10.37188/CO.2020-0153
引用本文: 田慧军, 刘巧莉, 岳恒, 胡安琪, 郭霞. 高比探测率和高速石墨烯/n-GaAs复合结构的光电探测器[J]. 中国光学. doi: 10.37188/CO.2020-0153
TIAN Hui-jun, LIU Qiao-li, YUE Heng, HU An-qi, GUO Xia. Hybrid graphene/n-GaAs photodiodes with high specific detectivity and high speed[J]. Chinese Optics. doi: 10.37188/CO.2020-0153
Citation: TIAN Hui-jun, LIU Qiao-li, YUE Heng, HU An-qi, GUO Xia. Hybrid graphene/n-GaAs photodiodes with high specific detectivity and high speed[J]. Chinese Optics. doi: 10.37188/CO.2020-0153

高比探测率和高速石墨烯/n-GaAs复合结构的光电探测器

doi: 10.37188/CO.2020-0153
详细信息
  • 中图分类号: TN364

Hybrid graphene/n-GaAs photodiodes with high specific detectivity and high speed

More Information
    Author Bio:

    TIAN Hui-jun (1984—), PhD student, Institute of Laser Engineering, Beijing University of Technology, China. His research interests focus on graphene-based photodetectors. E-mail: tianhj@emails.bjut.edu.cn

    GUO Xia (1974—), Professor, School of Electronic Engineering, Beijing University of Posts and Telecommunications, China. Her research interests are on high-response PIN diodes, high speed VCSELs and ultrahigh-sensitive photodetectors in Graphene. E-mail: guox@bupt.edu.cn

    Corresponding author: anqihu@bupt.edu.cnguox@bupt.edu.cn
  • 摘要: 混合结构的石墨烯/半导体光电晶体管因其超高的响应度而备受关注。然而,该类光电晶体管通过源-漏电极测试得到的比探测率(D*)容易受到1/f噪声的限制。本文制备了混合结构的石墨烯/GaAs光电探测器,通过源-栅电极测得D*大约为1.82×1011 Jones,与通过源-漏电极测量相比,D*提高了约500倍。这可归因于界面上肖特基势垒对载流子俘获和释放过程的屏蔽作用。此外,探测器的上升时间和下降时间分别是4 ms和37 ms,响应速度相应地提高了2个数量级。该工作为制备高比探测率和高速的光电探测器提供了一种新的思路。
  • Figure  1.  (a) Schematic diagram of the graphene/n-GaAs photodetector. The optical and electrical performances were measured by source-gate electrodes. (b) Energy band diagram of the graphene/n-GaAs heterojunction with the Schottky barrier height ΦB of the graphene/GaAs junction of ~0.7 eV. The interface states are depicted at the interface, illustrating that the carrier trapped photons at the graphene/GaAs interface during carrier transport through the junction. (c) Measurement result of the Raman spectrum of graphene on the GaAs substrate. (d) Spectral response of the photodiode under zero bias voltage.

    Figure  2.  (a) Current versus voltage curves of the device under different light powers. (b) The relationship between photocurrent and photovoltage (Voc) with the incident light’s power in the self-driven mode. (c) Responsivity and D* versus illumination power under a zero bias voltage. (d) Illustration of the carrier trapping and detrapping processes at the interface of the graphene/GaAs interface, which is the main source of 1/f noise.

    Figure  3.  The response time of the photodiode at a zero bias voltage under a laser power of 136 μW where τr is ~4 ms and τf is ~37 ms.

  • [1] KOPPENS F H L, MUELLER T, AVOURIS P, et al. Photodetectors based on graphene, other two-dimensional materials and hybrid systems[J]. Nature Nanotechnology, 2014, 9(10): 780-793. doi:  10.1038/nnano.2014.215
    [2] NAIR R R, BLAKE P, GRIGORENKO A N, et al. Fine structure constant defines visual transparency of graphene[J]. Science, 2008, 320(5881): 1308. doi:  10.1126/science.1156965
    [3] GUO X T, WANG W H, NAN H Y, et al. High-performance graphene photodetector using interfacial gating[J]. Optica, 2016, 3(10): 1066-1070. doi:  10.1364/OPTICA.3.001066
    [4] GREBENCHUKOV A N, ZAITSEV A D, KHODZITSKY M K. Optically controlled narrowband terahertz switcher based on graphene[J]. Chinese Optics, 2018, 11(2): 166-173. doi:  10.3788/co.20181102.0166
    [5] HU A Q, TIAN H J, LIU Q L, et al. Graphene on self-assembled InGaN quantum dots enabling ultrahighly sensitive photodetectors[J]. Advanced Optical Materials, 2019, 7(8): 1801792. doi:  10.1002/adom.201801792
    [6] LIU Q L, TIAN H J, LI J W, et al. Hybrid graphene/Cu2O quantum dot photodetectors with ultrahigh responsivity[J]. Advanced Optical Materials, 2019, 7(20): 1900455. doi:  10.1002/adom.201900455
    [7] GONG X, TONG M H, XIA Y J, et al. High-detectivity polymer photodetectors with spectral response from 300 nm to 1450 nm[J]. Science, 2009, 325(5948): 1665-1667. doi:  10.1126/science.1176706
    [8] WANG G SH, LU H, CHEN D J, et al. High quantum efficiency GaN-based p-i-n ultraviolet photodetectors prepared on patterned sapphire substrates[J]. IEEE Photonics Technology Letters, 2013, 25(7): 652-654. doi:  10.1109/LPT.2013.2248056
    [9] BALANDIN A A. Low-frequency 1/f noise in graphene devices[J]. Nature Nanotechnology, 2013, 8(8): 549-555. doi:  10.1038/nnano.2013.144
    [10] LU Y H, FENG S R, WU ZH Q, et al. Broadband surface plasmon resonance enhanced self-powered graphene/GaAs photodetector with ultrahigh detectivity[J]. Nano Energy, 2018, 47: 140-149. doi:  10.1016/j.nanoen.2018.02.056
    [11] TIAN H J, HU A Q, LIU Q L, et al. Interface-induced high responsivity in hybrid graphene/GaAs photodetector[J]. Advanced Optical Materials, 2020, 8(8): 1901741. doi:  10.1002/adom.201901741
    [12] HU W D, LI Q, CHEN X SH, et al. Recent progress on advanced infrared photodetectors[J]. Acta Physica Sinica, 2019, 68(12): 120701. (in Chinese)
    [13] CHEN Y Y, WANG C H, CHEN G S, et al. Self-powered n-MgxZn1−xO/p-Si photodetector improved by alloying-enhanced piezopotential through piezo-phototronic effect[J]. Nano Energy, 2015, 11: 533-539. doi:  10.1016/j.nanoen.2014.09.037
    [14] FAUSKE V T, HUH J, DIVITINI G, et al. In situ heat-induced replacement of GaAs nanowires by Au[J]. Nano Letters, 2016, 16(5): 3051-3057. doi:  10.1021/acs.nanolett.6b00109
    [15] ZHANG X T, ZHANG L N, CHAN M S. Doping enhanced barrier lowering in graphene-silicon junctions[J]. Applied Physics Letters, 2016, 108(26): 263502. doi:  10.1063/1.4954799
    [16] LI X Q, LIN SH SH, LIN X, et al. Graphene/h-BN/GaAs sandwich diode as solar cell and photodetector[J]. Optics Express, 2016, 24(1): 134-145. doi:  10.1364/OE.24.000134
    [17] CANCADO L G, JORIO A, FERREIRA E H M, et al. Quantifying defects in graphene via Raman spectroscopy at different excitation energies[J]. Nano Letters, 2011, 11(8): 3190-3196. doi:  10.1021/nl201432g
    [18] HAO Y F, WANG Y Y, WANG L, et al. Probing layer number and stacking order of few-layer graphene by Raman spectroscopy[J]. Small, 2010, 6(2): 195-200. doi:  10.1002/smll.200901173
    [19] DI BARTOLOMEO A. Graphene Schottky diodes: an experimental review of the rectifying graphene/semiconductor heterojunction[J]. Physics Reports, 2016, 606: 1-58. doi:  10.1016/j.physrep.2015.10.003
    [20] TONGAY S, LEMAITRE M, MIAO X, et al. Rectification at graphene-semiconductor interfaces: zero-gap semiconductor-based diodes[J]. Physics Review X, 2012, 2(1): 011002.
    [21] LIN F, CHEN SH W, MENG J, et al. Graphene/GaN diodes for ultraviolet and visible photodetectors[J]. Applied Physics Letters, 2014, 105(7): 073103. doi:  10.1063/1.4893609
    [22] NI ZH Y, MA L L, DU S CH, et al. Plasmonic silicon quantum dots enabled high-sensitivity ultrabroadband photodetection of graphene-based hybrid phototransistors[J]. ACS Nano, 2017, 11(10): 9854-9862. doi:  10.1021/acsnano.7b03569
    [23] ZENG L H, WU D, LIN SH H, et al. Controlled synthesis of 2D palladium diselenide for sensitive photodetector applications[J]. Advanced Functional Materials, 2019, 29(1): 1806878. doi:  10.1002/adfm.201806878
    [24] MEIRZADEH E, CHRISTENSEN D V, MAKAGON E, et al. Surface pyroelectricity in cubic SrTiO3[J]. Advanced Materials, 2019, 31(44): 1904733. doi:  10.1002/adma.201904733
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    [2] Xiao-ying HE, Jian DONG, Shuai HU, Yan HE, Ben-shun LV, Xin-xin LUAN, Chong LI, 安琪 胡, Zong-hai HU, Xia GUO.  High-speed 850 nm vertical-cavity surface-emitting lasers with BCB planarization technique . 中国光学, doi: 10.3788/CO.20181102.0190
    [3] Alexander N GREBENCHUKOV, Anton D ZAITSEV, Mikhail K KHODZITSKY.  Optically controlled narrowband terahertz switcher based on graphene . 中国光学, doi: 10.3788/CO.20181102.0166
    [4] 陈勰宇, 田震.  石墨烯太赫兹波动态调制的研究进展 . 中国光学, doi: 10.3788/CO.20171001.0086
    [5] 谢世伟, 肖啸, 谭建军, 刘愈, 张志友, 杜惊雷, 高福华.  基于石墨烯基电极染料敏化太阳能电池的研究进展 . 中国光学, doi: 10.3788/CO.20140701.047
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出版历程
  • 收稿日期:  2020-09-01
  • 修回日期:  2020-09-14
  • 网络出版日期:  2020-12-07

Hybrid graphene/n-GaAs photodiodes with high specific detectivity and high speed

doi: 10.37188/CO.2020-0153
    通讯作者: anqihu@bupt.edu.cnguox@bupt.edu.cn
  • 中图分类号: TN364

摘要: 混合结构的石墨烯/半导体光电晶体管因其超高的响应度而备受关注。然而,该类光电晶体管通过源-漏电极测试得到的比探测率(D*)容易受到1/f噪声的限制。本文制备了混合结构的石墨烯/GaAs光电探测器,通过源-栅电极测得D*大约为1.82×1011 Jones,与通过源-漏电极测量相比,D*提高了约500倍。这可归因于界面上肖特基势垒对载流子俘获和释放过程的屏蔽作用。此外,探测器的上升时间和下降时间分别是4 ms和37 ms,响应速度相应地提高了2个数量级。该工作为制备高比探测率和高速的光电探测器提供了一种新的思路。

English Abstract

田慧军, 刘巧莉, 岳恒, 胡安琪, 郭霞. 高比探测率和高速石墨烯/n-GaAs复合结构的光电探测器[J]. 中国光学. doi: 10.37188/CO.2020-0153
引用本文: 田慧军, 刘巧莉, 岳恒, 胡安琪, 郭霞. 高比探测率和高速石墨烯/n-GaAs复合结构的光电探测器[J]. 中国光学. doi: 10.37188/CO.2020-0153
TIAN Hui-jun, LIU Qiao-li, YUE Heng, HU An-qi, GUO Xia. Hybrid graphene/n-GaAs photodiodes with high specific detectivity and high speed[J]. Chinese Optics. doi: 10.37188/CO.2020-0153
Citation: TIAN Hui-jun, LIU Qiao-li, YUE Heng, HU An-qi, GUO Xia. Hybrid graphene/n-GaAs photodiodes with high specific detectivity and high speed[J]. Chinese Optics. doi: 10.37188/CO.2020-0153
    • Graphene with atomic layer thickness has attracted worldwide attention because of its unique electronic, optoelectronic, mechanical properties[1,2]. Recently, hybrid graphene/semiconductor phototransistors have been increasingly investigated for optoelectronic applications because of their ultrahigh responsivity[3-5]. In such structures, photogenerated carriers separate at the interface of the graphene/semiconductor junction. Because of the photogating effect, the responsivity obtained via such photoconductivity-based devices, whose photocurrent was measured from source-drain electrodes, can be as high as 1010 A/W at 0.19 V[6]. The corresponding specific detectivity (D*), which characterizes the sensitivity of a photodetector, has been reported to be as high as 1.4×1012 Jones[6]. However, based on a detailed comparison of the magnitude of three types of noise[6,7], it can be found that the D* of such phototransistors is mainly limited by 1/f noise[6], not the thermal noise or the shot noise, which play dominant roles in conventional photovoltaic-type semiconductor photodiodes[7-8]. The 1/f noise in this system mainly originates from the carrier trapping and detrapping processes at the graphene/semiconductor interface[9]. In other words, the D* of photoconductivity-based devices ranges from ~108 Jones to ~1014 Jones, which brings great enhancement in responsivity[3-6]. A high density of trapping centers at the interface also results in severe persistent photoconduction, and a relatively long transient response time. Generally, the reported transient response time of such hybrid phototransistors is in the order of seconds or even milliseconds[5,6]. These photodetectors need to work under external bias voltage, whose applications are usually limited because of the large 1/f noise. To overcome these limitations, new types of photodetectors are required[10].

      For the direction perpendicular to the graphene/semiconductor junction, whose photocurrent is measured by source-gate electrodes, interface traps play only a small role in the entire current transport loop. The source of 1/f noise is lessened and the persistent photoconductive effect can be relieved, which induces a high D* and high response speed[11]. These photodetectors with low power consumption, low cost and high sensitivity can satisfy practical applications’ requirements such as in visible light imaging and large-scale integrated circuitry[12,13]. For photovoltaic-type devices, the D* ranges from ~1010 Jones to ~1013 Jones, which originates from there being lower noise under zero voltage[10]. Moreover, the reported transient response time of photovoltaic-type devices is in the order of microseconds[11]. In this paper, the photocurrent measured from the source-gate electrodes of a hybrid graphene/n-GaAs photodiode demonstrated improved D* and response speed. This work is promising for developing low power consumption visible-light photodetectors with high sensitivity that are ideal in applications like imaging.

    • Sidoped with a GaAs substrate with an electron concentration of ~1×1018 cm−3 was selected for this study. Au/Ge/Ni/Au (10/10/5/100 nm) electrodes were deposited on the back of the n-GaAs substrate and then treated via rapid thermal annealing at 430 ºC for 35 s in an N2 environment to form ohmic contact[14]. The graphene was synthesized via chemical vapor deposition on Cu foil and then transferred to the front of the GaAs substrate using polymethylmethacrylate (PMMA) as the supporting film. Thus, a hybrid graphene/n-GaAs photodiode was obtained after metal deposition. The Raman spectrum was tested using a Renishaw Invia Raman microscope with a 514-nm laser source. Electrical measurements were carried out using a Keithley 4200. Illumination was provided by a laser at 650 nm with a series of neutral density filters under ambient conditions. A Si photodiode (Hamamatsu S2387) was used to calibrate the power.

    • Figure 1(a) demonstrates the schematic diagram of the graphene/n-GaAs photodiode studied in this work. The optical and electrical performances were measured from source-gate electrodes at room temperature. Figure 1(b) illustrates the energy band diagram of the graphene/n-GaAs heterojunction, where a Schottky barrier forms at the interface. Because of the different work functions between graphene (~4.8 eV) and n-GaAs (~4.1 eV)[15-16], the energy band bends upward and a built-in electric field is formed at the interface between graphene and n-GaAs with a barrier height of ~0.7 eV. The photoexcited electron-hole pairs separate under the function of the built-in field when light illuminates the sample. Due to the high surface state density of the GaAs material, the photoexcited holes fill up its surface states first because they accumulate near the interface, as illustrated in Figure 1(b). The Raman spectrum of the graphene is as shown in Figure 1(c). The G and 2D bands are located at 1582.9 cm−1 and 2683.8 cm−1, respectively. The absence of a D band indicates that there are few defects[17]. The intensity ratio of the 2D band to the G band is above 3, which causes monolayer characteristics of graphene[18]. Figure 1(d) shows the spectral response of the device. Under a zero bias voltage, the spectral responsivity of the photodiode was shown for an incident light power of ~200 nW over the range of 300~1100 nm. The responsivity exceeded 75 mA/W in the visible light region (380~760 nm). The cutoff wavelength was around 870-nm which corresponded to the GaAs edge of the energy band.

      Figure 1.  (a) Schematic diagram of the graphene/n-GaAs photodetector. The optical and electrical performances were measured by source-gate electrodes. (b) Energy band diagram of the graphene/n-GaAs heterojunction with the Schottky barrier height ΦB of the graphene/GaAs junction of ~0.7 eV. The interface states are depicted at the interface, illustrating that the carrier trapped photons at the graphene/GaAs interface during carrier transport through the junction. (c) Measurement result of the Raman spectrum of graphene on the GaAs substrate. (d) Spectral response of the photodiode under zero bias voltage.

      Figure 2(a) (Color online) shows the current-voltage (I-V) measurement results of the photodiodes illuminated under a 650-nm laser with different light intensities. All the curves demonstrate good rectification behavior due to the heterojunction formed between graphene and n-GaAs[19]. According to thermionic emission theory, current-voltage curves are expressed as below:

      $$I = {I_0}\left[\exp \left(\frac{{qV}}{{nkT}}\right) - 1\right]\quad,$$ (1)
      $${I_0} = AA^*{T^2}\exp \left(\frac{{ - q{\varPhi _{\rm{B}}}}}{{kT}}\right)\quad,$$ (2)

      where q is the charge, V is the bias voltage, k is the Boltzmann constant, T is the temperature, n is the ideality factor, I0 is the reverse saturation current, A is the photosensitive area of the photodiode, A* is the effective Richardson constant of n-GaAs (12.1 A·K−2cm−2)[18], and ΦB is the barrier height of the Schottky junction[20-21]. According to the fitting results, ΦB and n were respectively extracted to be 0.65 eV and 1.89 for the dark curve, which is almost consistent with the above theoretically determined value. The extracted data of n, which is much larger than 1, indicates that the recombination process with the assistance of interfacial states dominates the carrier transport process at the graphene/GaAs interface.

      Figure 2.  (a) Current versus voltage curves of the device under different light powers. (b) The relationship between photocurrent and photovoltage (Voc) with the incident light’s power in the self-driven mode. (c) Responsivity and D* versus illumination power under a zero bias voltage. (d) Illustration of the carrier trapping and detrapping processes at the interface of the graphene/GaAs interface, which is the main source of 1/f noise.

      The photocurrent (Iphoto) increases linearly from 49.7 nA to 2.93 μA as the illumination power increased from 492 nW to 136 μW at a zero bias voltage, as shown in Figure 2(b). The photovoltage (Voc) increased from 0.12 to 0.275 V when the power increased from 492 nW to 136 μW. Figure 2(c) shows the responsivity versus the power of the incident light of the device. The responsivity (R) of the photodiode is defined by the equation

      $$R = {I_{{\rm{photo}}}}/{P_{{\rm{in}}}}\quad,$$ (3)

      where Pin is the incident light power. Under a zero bias voltage, the highest responsivity was 95 mA/W. It can be seen that the responsivity of the photodiode slightly decreased with an increase in power. This can be attributed to a reduction in the built-in field when there is an increasing number of photogenerated carriers, which forms an electric field that opposes the built-in field. When light illuminates the graphene/n-GaAs photodetector, GaAs absorbs the photons with energy larger than its bandgap and induces electron-hole pairs, which are separated by the function of the built-in field. Photo-induced holes move towards graphene, while photo-induced electrons move towards GaAs. The photo-induced holes fill up the surface states first because of the high surface state density of the GaAs material. Then the other photo-induced holes can be driven into graphene and collected by the electrode to generate the photoresponse.

      D* is one of the important parameters for a photodetector, which is defined as

      $$D^* = {(AB)^{1/2}}/{P_{\rm{N}}}\quad,$$ (4)

      where A is the area (0.01 cm2) of the device, B is the electrical bandwidth, and PN is the noise’s equivalent power. PN is expressed as

      $${P_{\rm{N}}} = {({S_{\rm{I}}})^{1/2}}/R\quad,$$ (5)

      where R is the responsivity and $S_{\rm{I}} $ is the mean-square of the noise’s current in the dark. According to the theory of noise, $S_{\rm{I}} $ is the total sum of the 1/f noise ($S_{\rm{I}} $(1/f)), the shot noise ($S_{\rm{I}} $(shot)), and the thermal noise ($S_{\rm{I}} $(thermal))[22], which can be calculated using

      $${S_{\rm{I}}} = {S_{\rm{I}}}({\rm{1/}}f) + {S_{\rm{I}}}({\rm{shot}}) + {S_{\rm{I}}}({\rm{thermal}}).$$ (6)

      At a modulation frequency of 1 Hz, the $S_{\rm{I}} $(1/f) is ~10−35 A2·Hz−1, which can be represented by the following equation:

      $${S_{\rm{I}}}({\rm{1/}}f) = \frac{{{{\left| {I(f)} \right|}^2}}}{{{F_{\rm{S}}}N}}\quad,$$ (7)

      where I(f) is the discrete Fourier transform of the dark current waveform I(t), $F_{\rm{S}}$ is the sampling rate, and N is the number of data points. The $S_{\rm{I}} $(shot) is calculated to be ~1.04×10−27 A2·Hz−1 by using

      $${S_{\rm{I}}}({\rm{shot}}) = 2q{I_{\rm{d}}}\quad,$$ (8)

      where q is the elemental charge and Id is the dark current of the device. $S_{\rm{I}} $ (thermal) is calculated to be ~1.66×10−27 A2·Hz−1 at room temperature by using Nyquist’s equation, represented as

      $${S_{\rm{I}}}({\rm{thermal}}) = 4kT/{R_{\rm{S}}}\quad,$$ (9)

      where k is the Boltzmann constant, T is the temperature, and ${R_{\rm{S}}} $ is the differential resistance of the device in the dark. As shown in Figure 2(c), D* at 0 V was observed to decrease with increasing light power because of the reduction of responsivity. The maximum D* of the device was 1.82×1011 Jones, which is 562 times higher than the source-drain signal of a graphene/GaAs phototransistor that was fabricated in the same experiment conditions[11]. The obvious improvement of D* is attributed to the screen effect from the Schottky barrier. Comparing the two types of carrier transport processes, as illustrated in Figure 2(d) and 1(b), the 1/f noise dominates the mean square noise $S_{\rm{I}} $ for the source-drain photocurrent because of the trapping and detrapping processes at the interface during carrier transport, which is related to the carrier number and mobility fluctuation[9]. The 1/f noise of the source-gate measurement, as illustrated in Figure 1(b), was cut off because the interfacial states were filled by photoexcited holes first. Only then were the other photoexcited holes allowed the transport electrodes. The trapping barrier can be lowered only at elevated temperatures and bias. Because the source of noise was changed from well-known 1/f noise to thermal noise, D* improved greatly.

      Figure 3 shows the transient response measurement of the device under a laser power of 136 μW at 0 V at room temperature[23]. It should be noted that there is a peak when the light turns on, which can be repeated. We attributed it to the pyroelectricity effect caused by the electrical response to a sudden tiny temperature change when the light was turned on[24]. The rise time (τr) and decay time (τf) were measured to be 4 ms and 37 ms, respectively. The relatively long decay time after switching off the light indicates that it took more time for carriers to be transported from the GaAs semiconductor to the depletion region via diffusion and then be injected into graphene and recombined. The fast response was attributed to the quick separation of photogenerated carriers by the built-in electric field at the interface. Compared with the results measured by source-drain electrodes, which respectively had a rise and decay time of 270 ms and 28.5 s[11], the transit response performance also improved by ~2 orders of magnitude.

      Figure 3.  The response time of the photodiode at a zero bias voltage under a laser power of 136 μW where τr is ~4 ms and τf is ~37 ms.

    • In this work, the optoelectronic performance of the graphene/n-GaAs structure measured by source-gate electrodes was described. Due to the trapping and detrapping processes, there was a maximum specific detectivity of 1.82×1011 Jones with a rise time of 4 ms and a decay time of 37 ms, achieved at 0 V at room temperature. We attribute the ~2 orders of magnitude improvement in specific detectivity and its corresponding response time to the screening of interfacial states given by the Schottky barrier.

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