High-performance Broadband Floating-base Bipolar

Transcription

1 High-performance Broadband Floating-base Bipolar Phototransistor Based on WSe 2 /BP/MoS 2 Heterostructure Hao Li a, Lei Ye b, *, Jianbin Xu a, * a Department of Electronic Engineering, Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China. b School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei , People s Republic of China * Corresponding author at: Department of Electronic Engineering, Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China. Fax: ; Tel: ; address: jbxu@ee.cuhk.edu.hk; leiye@hust.edu.cn; 1

2 Contents Figure S1. Transfer process of the hetero-junction Figure S2. EQE of the WSe 2 /BP/MoS 2 device illumined by three lasers with different wavelengths. Figure S3. Raman spectra on different positions of the WSe 2 /BP/MoS 2 device. Figure S4, AFM measurement of the thickness of device components. Figure S5. Continuously measured dark current with a sampling frequency of 100 Hz Figure S6. Current noise characterization of the WSe 2 /BP/MoS 2 device Calculation of specific detectivities Table S1. Summary of the theoretically predicted shot-noise limited detectivities and practically measured detectivities for the visible and near infrared regions for recently reported 2D material based photodetectors. Calculation of amplification factor 2

3 Transfer process of the device Figure S1. Transfer process of the hetero-junction Step 1: Firstly, few-layer WSe 2, MoS 2 and BP were mechanically exfoliated onto Si/SiO 2 chip respectively. Step 2: Secondly, two gold electrodes were formed by photolithography and thermal evaporation with the distance of 10 µm, the sample is then cut into small pieces Step 3: Thirdly, PMMA was spin-coated (1500 rpm for 40 s) on the WSe 2 (MoS 2, BP) samples and baked under 170 for 10 minutes as shown in Figure S1 (a). Step 4: Fourthly, the WSe 2 (MoS 2, BP) samples were then immersed into Hydrogen fluoride (48%) to etched away SiO 2. After SiO 2 totally etched, WSe 2 (MoS 2, BP) flakes were attached onto PMMA membrane and floating on the surface (as is shown in Figure S1 (b)). Step 5: Then we used a plastic holder with a hole to pick up the membrane, so as to 3

4 expose WSe 2 (MoS 2, BP) at the bottom surface. The sample can now be observed in optical microscope, the WSe 2 (MoS 2, BP) flakes can be clearly seen. The flake was then aligned and transferred onto the channel (Sequence: WSe 2, MoS2, BP) with the assistance of a photolithography machine to form the hetero-junction shown in Figure S1 (d). Step 5: After every transfer process, the PMMA membrane was etched away in acetic acid, leaving the heterojunction on SiO 2 chip. 4

5 Figure S2. EQE of the WSe 2 /BP/MoS 2 device under three lasers with different wavelengths. 5

6 Figure S3. Raman spectra of WSe 2, MoS 2, BP and the corresponding overlapped regions WSe 2 /BP and MoS 2 /BP. 6

7 Figure S4. (a) Optical graph of the device and the dash lines indicating the positions of the height profiles (b) WSe 2, (c) Black Phosphorus and (d) MoS 2 7

8 Figure S5. Continuously measured dark current with a sampling frequency of 100 Hz Figure S6. Current noise characterization of the WSe 2 /BP/MoS 2 device. 8

9 Calculation of specific detectivity Specific detectivity D* = (A f) 1/2 /NEP, where A is the area of the photodetector, f is the electrical bandwidth in Hz (fixed as 1 Hz in this case), and NEP is the noise equivalent power. The area of the junction is extracted as 28 µm 2, with the help of photoshop and matlab. For V ce =3 V: I dark =2.24nA Shot noise limit detectivities: I shot =(2qI dark f) 1/2 = A Noise Equivalent Power NEP=Ishot/R For 532 nm: Detectivity D*shot-noise-limit=(A f) 1/2 /NEP=(A f) 1/2 *R 532 /I shot =(28µm 2 ) 6.32A/W / A = Jones For 1550nm D*shot-noise-limit = (A f) 1/2 /NEP = (A f) 1/2 R 1550 /Ishot=(28 µm 2 ) 1.12A/W / A = Jones Practically measured detectivities: Extracted Noise Current (Mean Value): I noise = 3.387pA Noise Equivalent Power NEP=I noise /R For 532 nm: 9

10 Detectivity D*=(A f) 1/2 /NEP=(A f) 1/2 *R 532 /I noise =(28µm 2 ) 6.32A/W / = Jones For 1550nm D* = (A f) 1/2 /NEP = (A f) 1/2 R 1550 /I noise =(28 µm 2 ) 1.12A/W / A = Jones 10

11 Visible Region Near Infrared Region Theoretical Measured Theoretical Measured Detectivity Detectivity Detectivity Detectivity Absorption Medium (Jones) (Jones) (Jones) (Jones) WSe 2/BP/MoS 2 (this work) Graphene/Si with Au triangles 1 ~ Graphene/Carbon Nanotube Graphene/Silicon Graphene/Silicon MoS 2 5 ~ MoS 2 encapsulated by HfO InSe MoS 2/MAPbI Graphene/MAPbI 9 3 ~ WS 2/Peroskite MoS 2 Quantum Dots Few Layer GaS 12 ~ BP/MoS Graphene/Germanium MoS 2/Graphene S-defect doped MoS Table S1. Summary of the theoretically predicted shot-noise limited detectivities and practically measured detectivities for the visible and near infrared regions for recently reported 2D material based photodetectors. 11

12 Calculation of amplification factor 1 β ( W / 2 τ D ) + ( D W N / D L N ) 2 B B P N B D P P A τ B is the minority carrier lifetime in the base which is contributed by the photo-generated carries. The lifetime of photogenerated carriers in Black phosphorus is 100 ps [17]. The D N and D P are the carrier diffusion coefficients in the base, which are both 1300 cm 2 s -1 [17]. L P is the diffusion length of holes in the emitter (MoS 2 ), which as calculated by = = / = cm Where for few layer MoS 2 is 1.27 ns [18] and the corresponding diffusion coefficient is 20 cm 2 s -1 [19]. N A is the acceptor density in the base (Black Phosphorus) which is 1.03E13 cm -2 [20]. N D is the donor densities in the emitter (MoS 2 ), which is 3.57E11 cm -2 [21]. Substitute the data into the equation and we will have the result as below, for W B from 1 μ ~10μ :

13 References: (1) Chen, Z.; Li, X.; Wang, J.; Tao, L.; Long, M.; Liang, S.; Lau, K.; Shu, C.; Tsang, H. K.; Xu, J. B. Synergistic Effects of Plasmonics and Electrons Trapping in Graphene Short-Wave Infrared Photodetectors with Ultrahigh Responsivity. ACS nano (2) Lu, R.; Christianson, C.; Weintrub, B.; & Wu, J. Z. High photoresponse in hybrid graphene carbon nanotube infrared detectors. ACS applied materials & interfaces, 2013, 5(22), (3) An, X.; Liu, F.; Jung, Y. J.; Kar, S. Tunable graphene silicon heterojunctions for ultrasensitive photodetection. Nano letters, 2013, 13(3), (4) An, Y.; Behnam, A.; Pop, E.; Bosman, G.; Ural, A. Forward-bias diode parameters, electronic noise, and photoresponse of graphene/silicon Schottky junctions with an interfacial native oxide layer. Journal of Applied Physics, 2013, 118(11), (5) Choi, W.; Cho, M. Y.; Konar, A.; Lee, J. H.; Cha, G. B.; Hong, S. C.; Kim, S.; Kim, J.; Jena, D.; Joo, J.; Kim, S. High detectivity multilayer MoS 2 phototransistors with spectral response from ultraviolet to infrared. Advanced Materials, 2012, 24(43), (6) Kufer, D.; Konstantatos, G. Highly sensitive, encapsulated MoS 2 photodetector with gate controllable gain and speed. Nano letters, 2015,15(11), (7) Tamalampudi, S. R.; Lu, Y. Y.; Kumar U, R.; Sankar, R.; Liao, C. D.; Moorthy B. K.; C. Cheng; Chou, F.C.; Chen, Y. T. High performance and bendable few-layered InSe photodetectors with broad spectral response. Nano letters, 2014,14(5),

14 (8) Kang, D. H.; Pae, S. R.; Shim, J.; Yoo, G.; Jeon, J. ; Leem, J. W.; Yu, J.; Lee, S.; Shin, B.; Park, J. H. An Ultrahigh Performance Photodetector based on a Perovskite Transition Metal Dichalcogenide Hybrid Structure. Advanced Materials, 2016,28(35), (9) Lee, Y.; Kwon, J.; Hwang, E.; Ra, C. H.; Yoo, W. J.; Ahn, J. H.; Park, J.H.; Cho, J. H. High performance perovskite graphene hybrid photodetector. Advanced materials, 2015, 27(1), (10) Ma, C.; Shi, Y.; Hu, W.; Chiu, M. H.; Liu, Z.; Bera, A.; Li, F.; Wang, H.; Li, L.J.; Wu, T. Heterostructured WS2/CH3NH3PbI3 Photoconductors with Suppressed Dark Current and Enhanced Photodetectivity. Advanced Materials, 2016, 28(19), (11) Mukherjee, S.; Maiti, R.; Katiyar, A. K.; Das, S.; Ray, S. K. Novel Colloidal MoS 2 Quantum Dot Heterojunctions on Silicon Platforms for Multifunctional Optoelectronic Devices. Scientific Reports, 2016, 6. (12) Hu, P.; Wang, L.; Yoon, M.; Zhang, J.; Feng, W.; Wang, X.; Wen, Z.; J.C. Idrobo; Y. Miyamoto; D.B. Geohagen; Xiao, K. Highly responsive ultrathin GaS nanosheet photodetectors on rigid and flexible substrates. Nano letters, 2013, 13(4), (13) Ye, L.; Li, H.; Chen, Z. F.; Xu, J. B. Near-infrared photodetector based on MoS 2 /black phosphorus heterojunction. ACS Photonics, 2016, 3(4), (14) Zeng, L. H.; Wang, M. Z.; Hu, H.; Nie, B.; Yu, Y. Q.; Wu, C. Y.; Wang, L.; Hu, J. G.; Xie, C.; Liang, F.X.; Luo, L. B. Monolayer graphene/germanium Schottky junction as high-performance self-driven infrared light photodetector. ACS applied materials & 14

15 interfaces, 2013, 5(19), (15) Vabbina, P.; Choudhary, N.; Chowdhury, A. A.; Sinha, R.; Karabiyik, M.; Das, S.; Choi, W.; Pala, N. Highly sensitive wide bandwidth photodetector based on internal photoemission in CVD grown p-type MoS 2 /graphene Schottky junction. ACS applied materials & interfaces, 2015, 7(28), (16) Xie, Y.; Zhang, B.; Wang, S.; Wang, D.; Wang, A.; Wang, Z.; Yu, H.; Zhang, H.; Chen, Y.; Zhao, M.; Mei, L.; Wang, J.; Huang, B. Ultrabroadband MoS 2 Photodetector with Spectral Response from 445 to 2717 nm. Advanced Materials (17) He, J.; He, D.; Wang, Y.; Cui, Q.; Bellus, M. Z.; Chiu, H. Y.; Zhao, H. Exceptional and anisotropic transport properties of photocarriers in black phosphorus. ACS nano, 2015, 9(6), (18) Choi, W.; Cho, M. Y.; Konar, A.; Lee, J. H.; Cha, G. B.; Hong, S. C.; Kim, S. High detectivity multilayer MoS 2 phototransistors with spectral response from ultraviolet to infrared. Advanced materials, 2012, 24(43), (19) Ganatra, R.; and Zhang, Q. Few-layer MoS 2 : a promising layered semiconductor. ACS nano, 2014,8.5, (20) Ge, S.; Li, C.; Zhang, Z.; Zhang, C.; Zhang, Y.; Qiu, J.; Sun, D. Dynamical evolution of anisotropic response in black phosphorus under ultrafast photoexcitation. Nano letters, 2015, 15(7), (21) Kwak, J. Y.; Hwang, J.; Calderon, B.; Alsalman, H.; Munoz, N.; Schutter, B.; Spencer, M. G. Electrical characteristics of multilayer MoS 2 FET s with MoS 2 /graphene heterojunction contacts. Nano letters, 2014, 8,