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Abstract
Solar-blind deep-ultraviolet communication (SDUC) presents a promising candidate for use in short-range military communications. Solar-blind photodetectors (PDs) form up the core component of the SDUC system’s receiving signal. In this study, an easy-to-integrate metal-semiconductor-metal (MSM)-type solar-blind PD is successfully fabricated based on the β-Ga2O3 film deposited on c-plane sapphire substrates by low-cost radio-frequency magnetron sputtering. The fabricated device exhibits a high responsivity of 1.93 A W−1, a remarkable detectivity of 6.53×1013 Jones, and a considerable photo-to-dark current ratio of 3.58×105. Most importantly, the device shows an extremely low dark current of 82 fA and an ultrafast response speed of 11/240 µs; one of the most ultra-high performances ever reported for β-Ga2O3 solar-blind PDs. In addition, it is the first time that a high-performance β-Ga2O3-based PD that is integrated into a self-made SDUC system as a signal receiver is demonstrated to transmit ASCII codes with such high accuracy and a data rate of 10 kbps. The results reported in this work serve as proof-of-concept for future applications of β-Ga2O3 solar-blind deep-ultraviolet photodetectors in secure communications.
© 2021 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Photodetectors (PDs) are devices that convert light signals into electrical signals. They have been widely applied in a variety of fields, including optical communications, biological sensing, and optical imaging [1–4]. Among these, optical communication possesses potential advantages such as having a small size, low power consumption and a large bandwidth, all of which are crucial aspects required for electronic digital products, industrial production, national defense, and aerospace [5,6]. Optical communication systems generally rely on light irradiation to transmit information, with their wavelengths ranging from deep-ultraviolet (DUV) to infrared (IR). Compared with traditional radio frequency (RF) wireless communication, optical communication technology, as an effective complementary technology to RF communication, can provide high speed, ultra-low latency, green, and low-cost communication services. This is due to its scattering and reflection abilities being unaffected by a variety of terrains and terrain features [7,8]. Use of IR communication in optical communication technology is relatively mature, however, the IR noise emitted by solar radiation and materials severely restrict applications of IR communication technology [9]. Due to its wide frequency spectrum, visible light communication technology has also been widely studied. Similarly to in IR communication, as transmission distance increases, the strong background noise leads to the reception of extremely weak light signals. To suppress stray background light, highly efficient optical filters are used for pre-processing. This includes the shaping and de-noising of the received visible light signals. However, tedious processing and high-costs mean that visible light communication still faces great challenges [10]. As we all know, when it enters the atmosphere, solar-blind deep-ultraviolet (200–280 nm) is absorbed by the ozone layer, and so there is almost no light in this waveband on the Earth's surface [4,11]. Thus, because of its higher signal-to-noise ratio and lower false alarm rate, solar-blind deep-ultraviolet communication (SDUC) has received more attention than IR/visible communication technology [6,7]. The development of high-performance solar-blind DUV PDs is an essential link in SDUC technology [6]. Up to now, various materials have been explored for the development of solar-blind DUV PDs, including AlxGax−1N [12], ZnMgO [13], diamond [14], and β-Ga2O3 [15]. Among them, a new type of β-Ga2O3 oxide semiconductor material has been shown to be able to avoid a complex alloying process, and has a direct bandgap of 4.9 eV and a corresponding absorption cut-off wavelength below ∼280 nm [16]. Furthermore, β-Ga2O3 also has a high critical breakdown field (∼ 8MV cm−2) and high thermal/chemical stability. These excellent characteristics show that β-Ga2O3 has strong application prospects for DUV photodetection. In recent years, with rapid developments in ultraviolet photodetection technology, solar-blind DUV PDs based on various device structures of β-Ga2O3 films have been extensively explored [16–20]. However, there are no reports on DUV communications constructed by Ga2O3-based solar-blind photodetectors.
In this study, an easy-to-integrate metal-semiconductor-metal (MSM)-type solar-blind DUV photodetector based on β-Ga2O3 thin film was fabricated. The photodetector exhibits high responsivity and detectivity, and has a considerable photo-to-dark current ratio. Even more notably, is that an extremely low dark current of 82 fA and an ultra-fast response speed of 11/240 µs have been achieved in the fabricated solar-blind photodetector. In addition, for the first time, a β-Ga2O3 photodetector has been successfully integrated into our self-made SDUC system as a DUV light signal receiver for the transmission of digital signals, causing the system to exhibit a faster transmission speed and excellent accuracy. The results indicate that the β-Ga2O3 photodetector is a promising candidate for future solar-blind DUV communication systems.
2. Experiment details
2.1 Material preparation and device fabrication
The β-Ga2O3 thin films were deposited on c-plane Al2O3 (0001) substrates by RF magnetron sputtering technology and subsequently underwent a high-temperature annealing process. A Commercialized Ga2O3 ceramic target (4N) was selected as the sputtering target. Before the deposition, the substrates were ultrasonically cleaned in deionized water, acetone, and alcohol for 10 minutes, respectively, after which they were dried in a flowing high-purity nitrogen atmosphere. During the deposition process meanwhile, the sputtering chamber base pressure is 5.0×10−4 Pa, and the argon flow rate, working pressure, sputtering power and time were set to 40 sccm, 2 Pa, 150 W and 1.5 h, respectively. Subsequently, the as-deposited Ga2O3 films were placed in a tube furnace and annealed in argon at 900 °C. Finally, two parallel Ti/Au electrodes measuring 300 µm in length, and with a spacing of 10 µm, were deposited on the β-Ga2O3 thin film’s surface by magnetron sputtering technique to fabricate the MSM photodetector.
2.2 Material and device characterization
The crystal structure of the β-Ga2O3 thin film was analyzed by X-ray diffractometer with Cu Kα line (λ=0.1540598 nm). The Raman spectra were collected by Raman spectrometer with 532 nm laser as the excitation light source. The transmission spectrum of the β-Ga2O3 thin film was recorded using an ultraviolet, visible, near-infrared spectrophotometer (U-4100). The surface morphology of the Ga2O3 film was characterized by AIST-NT Smart SPM atomic force microscope (AFM). A Keithley 4200 source meter was used to measure the photoelectric characteristics of the photodetector. The photoresponse spectrum of the photodetector was measured using a photoresponse test system. A Tektronix DPO 2024B oscilloscope was used for recording purposes. The transient photoresponse was examined by a 266 nm pulsed laser and Tektronix DPO 2024B oscilloscope. A MOS5072 oscilloscope was used to record the voltage signal in the solar-blind UV communication system. All characterizations were performed at room temperature.
3. Results and discussions
Figure 1(a) displays the X-ray diffraction (XRD) pattern of the β-Ga2O3 film deposited on the c-plane sapphire substrate. The diffraction peaks near to 18°, 38° and 58° correspond to (−201), (−402) and (−603) of the monoclinic β-Ga2O3 crystals (JCPDS Card No. 43-1012) [21], respectively. In addition, the (400), (002), (−313) and (−801) diffraction peaks of monoclinic β-Ga2O3 are also found. These indicate that the prepared film is β-phase Ga2O3. Figure 1(b) illustrates the Raman scattering spectrum of the β-Ga2O3 thin film. Except for the substrate peaks, only 9 out of the expected 15 patterns of β-Ga2O3 are observed. These are located at 145.7, 170, 201.4, 319.2, 347.9, 474.4, 630.3, 653.1 and 768.4 cm−1, respectively, which thereby further confirms that β-Ga2O3 thin film is successfully prepared by radio frequency magnetron sputtering and high-temperature annealing processes. These Raman peaks can be roughly divided into three categories [22]. The low frequency peaks, which correspond to a range of 150 cm−1 to 200 cm−1, are attributed to the translation and vibration of the GaO4 tetrahedron and Ga2O4 octahedral chain. The mid-frequency peaks (300∼500 cm−1) originate from the deformation of Ga2O4 octahedrons. The high-frequency peaks (500∼800 cm−1) are related to the bending and stretching of the GaO4 tetrahedron. Additionally, the peak located at 230.7 cm−1 is associated with the infrared mode Eu(TO/LO) [23]. The optical transmittance spectrum of the β-Ga2O3 film is shown in Fig. 1(c), and is accompanied by a sharp absorption edge in the ultraviolet region situated at ∼280 nm. Furthermore, the β-Ga2O3 film exhibits an ultrahigh transmittance of over 97% in the visible region with 380–760 nm, which thus lays a solid foundation for future developments of Ga2O3-based fully transparent optoelectronic devices. The optical bandgap of the β-Ga2O3 film calculated from the Tauc plot is about 4.9 eV, as displayed in the inset of Fig. 1(c). Figure 1(d) displays the atomic force microscope (AFM) image of β-Ga2O3 film surface with a scanning area of 20×20 µm2. As can be seen, the film shows quite smooth surface morphologies with a peak-to-valley roughness (Rpv) of 9.0 nm, and a root-mean-square roughness (RRMS) of 1.9 nm. In general, the β-Ga2O3 film prepared by low-cost magnetron sputtering and post-annealing technologies shows good structural and optical properties.
Fig. 1. (a) XRD pattern, (b) Raman spectrum, (c) transmittance spectrum, and d) AFM image of the β-Ga2O3 film. The inset of (c) is the Tauc plot for optical bandgap calculation.
To study the photoelectric properties of β-Ga2O3 thin film, the metal-semiconductor-metal (MSM) photodetector (PD) with a pair of parallel Ti/Au electrodes were fabricated, as shown in the inset of Fig. 2(a). This was achieved by using a shadow mask via vacuum magnetron sputtering. Figure 2(a) demonstrates the current-voltage (I-V) characteristic lines of the PD under dark conditions and 254 nm illumination. It is evident that the fabricated device shows an ultralow dark current of 82 fA at 10 V bias, comparable to the lowest dark current so far reported [24,25]. When the PD is exposed to 254 nm illumination of 500 µW·cm−2, the photocurrent of the device increases sharply to 29 nA, showing an ultrahigh photo-to-dark current ratio (PDCR) [26] of 3.58×105. Figure 2(b) shows the normalized responsivity (R) spectrum of the β-Ga2O3-based PD at 10 V bias. With a response spectrum cut-off at 262 nm, the device possesses prominent solar-blind DUV detection characteristics, which is different to its near no response when in the visible region with 380 nm−780 nm, thus suggesting that the device has good spectral selectivity. Figure 2(c) displays the response spectra of the PD under different bias voltages from 10 to 60 V, and the inset shows the maximum responsivity (Rmax∼252 nm) as a function of the bias voltage. As seen, with the increase in bias voltage, the Rmax of the PD increases in a linear fashion, while there is no sweep-out effect or carrier mobility saturation until 60 V [27]. Additionally, we also measured the photoresponse speed, which reflects the power of the PD to track the fast-changing optical signals. The single period photoresponse curve of the PD is modulated at frequency of 5 Hz under 266 nm pulse laser, as shown in Fig. 2(d). The rise time (τr) and decay time (τd) of the PD are calculated as 11 µs and 240 µs, respectively. Note that the response speed is at the forefront of the Ga2O3-based DUV photodetectors.
Fig. 2. (a) I−V characteristic curve of β-Ga2O3 solar-blind DUV PD under both dark and 254 nm illumination. The inset shows the schematic diagram of solar-blind DUV PD. (b) Normalized responsivity spectrum in logarithmic coordinates. (c) Normalized responsivity spectrum at different bias voltages. The inset shows the maximum responsivity as a function of the bias voltage. (d) Response curve of the DUV PD modulated at a frequency of 5 Hz under 266 nm pulsed laser.
As shown in Fig. 3, a more systematic measurement was carried out to further evaluate the optoelectronic performance of the β-Ga2O3-based DUV photodetector. Figure 3(a) exhibits the I-V characteristic lines of the PD under 254 nm light with different illumination intensities. The I-V characteristic lines are clearly non-linear, with the metal electrodes in back-to-back Schottky contact with the β-Ga2O3 film [28]. Due to the promotion of electron-hole pair generation by the high illumination density, the photocurrent of the PD increases with the increase of DUV illumination intensity [28]. To offer a deeper understanding of the above relationship, Fig. 3(b) displays the plot of the photocurrent to illumination intensity, which is extracted from Fig. 3(a) at 10 V. It is clear that the photocurrent has an almost linear dependence on illumination intensity. This can fit well with the power law (${I_{ph}} \propto {P^\theta }$) [7], where P is the light illumination intensity and ${\theta}$ is the exponent. Using fitting, the value of ${\theta}$ is shown to be 1.36. Being slightly larger than the ideal value (${\theta} = 1$), this suggests that trap states in β-Ga2O3 require less energy to excite electrons into the conduction band, which is to say, probability caused by parasitic gain of defects between electrodes and semiconductors and external power supply [29,30]. Meanwhile, the PDCR is positively correlated with the light intensity, as shown in Fig. 3(c). This is consistent with the variation pattern of the photocurrent to light intensity, with the PDCR being more than 105 under 254 nm light of 500 µW·cm−2 at 10 V
Fig. 3. (a) I–V characteristic lines of the solar-blind photodetector of β-Ga2O3 thin film under 254 nm illumination. (b) Photocurrent, (c) PDCR and (d) Responsivity and detectivity of the photodetector at 10 V with various illumination intensities. (e) Transient photoresponse of the device under 254 nm light with different illumination intensities and 365 nm illumination (500 µW/cm2).
So as to quantitatively evaluate the sensitivity of the β-Ga2O3 solar-blind DUV PD, both the responsivity (R) and detectivity (D*) under different illumination intensities at 10 V are calculated, as shown in Fig. 3(d). The R is defined as the photocurrent generated by the unit power of the incident DUV light on the effective area of the photodetector, which can be expressed as: [18]
For a better comparison, Table 1 shows some of the fabricated β-Ga2O3 MSM PD’s key parameters found in this work, as well as in other prior works. As seen, the device we prepared exhibits a good performance, including a high R of 1.93 A W−1, a high D* of 6.53×1013 Jones, and an outstanding PDCR of 3.58×105. Furthermore, an extremely low dark current of 82 fA and an ultrafast response speed of 11/240 µs are measured in this study. Overall, the presented β-Ga2O3 MSM PD, with its excellent performance, has the advantages of being easy to fabricate and being low-cost, which puts it in a promising position for future DUV detection applications, including meeting the requirements to receive optical signals as a component of the communication system.
Table 1. Summary of key parameters of Ga2O3 solar-blind DUV PD
With the increasingly tight wireless spectrum resources, the emerging solar-blind deep-ultraviolet communication (SDUC) system poses a huge expansion within the sphere of communication. Moreover, compared with radio-frequency communication and IR/visible light communication, SDUC offers great potential due to its anti-electromagnetic interference, high safety performance and ultrahigh signal-to-noise ratio [31]. To evaluate the SDUC capability of the photodetector, a SDUC proof-of-concept system is constructed for the first time. This is achieved by employing this study’s ultra-high performance β-Ga2O3 DUV PD as a signal receiver, as shown in Fig. 4. To modulate whether the LED light source is on/off, the digital data is first transformed into a control command by the driver (EP4CE6F17C8) that controls the MOSFET(LR7843) on/off switch. Then, the modulated light from the LED (255.5 nm) is received by the fabricated solar-blind DUV PD, whereby it outputs high- and low-level current signals. The photocurrent signals are amplified by the differential voltage preamplifier to input the driver (ADC chip), which can then convert the voltage signals into digital signals. Finally, those digital signals are collected by field programmable gate array (FPGA) and transmitted to a PC.
Fig. 4. Schematic diagram of the solar-blind DUV communication system based on β-Ga2O3 photodetector.
To investigate the transmission performance of the SDUC system, we tried to transmit the four letters “cqnu,” which are converted into American Standard Code for Information Interchange (ASCII) codes by the program. The control commands, “1” and “0” corresponding to the on/off switch of the MOSFET(LR7843), are sent by the driver (EP4CE6F17C8). The waveforms of the output digital data under different modulation frequencies and the corresponding real-time images displayed on the oscilloscope are shown in Fig. 5. As can be seen, all the waveforms exhibit the same response as the binary digital signal of “cqnu” and show no distortion when at a bit rate of up to 10 kbps. This indicates that the SDUC system based on the β-Ga2O3 photodetector possesses a fast transmission speed and excellent accuracy.
Fig. 5. The waveforms of the output digital data under different modulation frequencies and the corresponding real-time images displayed on the oscilloscope.
4. Conclusion
In summary, for the first time, a proof-of-concept model for the self-made solar-blind deep-ultraviolet communication system has been constructed using a β-Ga2O3-based photodetector as the signal receiver. An easy-to-integrate MSM-type photodetector was fabricated using a sputtered β-Ga2O3 film with two parallel Ti/Au electrodes. The fabricated device exhibits a high responsivity of 1.93 A W−1, a remarkable detectivity of 6.53×1013 Jones, and a considerable photo-to-dark current ratio of 3.58×105. Most importantly, an ultralow dark current of 82 fA and an ultrafast response speed of 11/240 µs were also measured. The solar-blind communication system shows high accuracy and a data rate of 10 kbps. These results lay down a path for the fabrication of high-performance photodetectors to be used for future applications of solar-blind DUV communications.
Funding
Natural Science Foundation of Chongqing (cstc2019jcyj-msxmX0237, cstc2020jcyj-msxmX0533, cstc2020jcyj-msxmX0557); Science and Technology Research Project of Chongqing Education Committee (KJQN201800501, KJQN201900542, KJQN20200051); National Natural Science Foundation of China (11904041).
Disclosures
The authors declare that they have no conflict of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. Q. Cai, H. You, H. Guo, J. Wang, B. Liu, Z. Xie, D. Chen, H. Lu, Y. Zheng, and R. Zhang, “Progress on AlGaN-based solar-blind ultraviolet photodetectors and focal plane arrays,” Light: Sci. Appl. 10(1), 1–31 (2021). [CrossRef]
2. J. Chen, W. Ouyang, W. Yang, H. He J, and X. Fang, “Recent progress of heterojunction ultraviolet photodetectors: materials, integrations, and applications,” Adv. Funct. Mater. 30, 1909909 (2020). [CrossRef]
3. C. Xie, X. Lu, X. Tong, Z. Zhang, F. Liang, L. Liang, L. Luo, and Y. Wu, “Recent progress in solar-blind deep-ultraviolet photodetectors based on inorganic ultrawide bandgap semiconductors,” Adv. Funct. Mater. 29, 1806006 (2019). [CrossRef]
4. X. Chen, F. Ren, S. Gu, and J. Ye, “Review of gallium-oxide-based solar-blind ultraviolet photodetectors,” Photonics Res. 7(4), 381 (2019). [CrossRef]
5. G. Cen, Y. Liu, C. Zhao, G. Wang, Y. Fu, G. Yan, Y. Yuan, C. Su, Z. Zhao, and W. Mai, “Atomic-layer deposition-assisted double-side interfacial engineering for high-performance flexible and stable CsPbBr3 perovskite photodetectors toward visible light communication,” Small 15, 1902135 (2019). [CrossRef]
6. C. Lin, Y. Lu, Y. Tian, C. Gao, M. Fan, X. Yang, L. Dong, and C. Shan, “Diamond based photodetectors for solar-blind communication,” Opt. Express 27(21), 29962 (2019). [CrossRef]
7. H. Fang, C. Zheng, L. Wu, Y. Li, J. Cai, M. Hu, X. Fang, R. Ma, Q. Wang, and H. Wang, “Solution-processed self-powered transparent ultraviolet photodetectors with ultrafast response speed for high-performance communication system,” Adv. Opt. Mater. 29, 1809013 (2019). [CrossRef]
8. B. Ouyang, H. Zhao, L. Wang Z, and Y. Yang, “Dual-polarity response in self-powered ZnO NWs/Sb2Se3 film heterojunction photodetector array for optical communication,” Nano Energy 68, 104312 (2020). [CrossRef]
9. Z. Xu and M. Sadler B, “Ultraviolet communications: potential and state-of-the-art,” IEEE Commun. Mag. 46(5), 67–73 (2008). [CrossRef]
10. C O’Brien D, L Zeng, L Minh H, G Faulkner, W Walewski J, and S Randel, “Visible light communications: Challenges and possibilities,” presented at the Photonics Conference International Symposium on Personal, Indoor and Mobile Radio Communications, Cannes France Sept 2018, 1–5
11. Y. Qin, L. Li, X. Zhao, S. Tompa G, H. Dong, G. Jian, Q. He, P. Tan, X. Hou, Z. Zhang, S. Yu, H. Sun, G. Xu, X. Miao, K. Xue, S. Long, and M. Liu, “Metal–semiconductor–metal ɛ-Ga2O3 solar-blind photodetectors with a record-high responsivity rejection ratio and their gain mechanism,” ACS Photonics 7(3), 812–820 (2020). [CrossRef]
12. E. Cicek, R. McClintock, Y. Cho C, B. Rahnema, and M. Razeghi, “AlxGa1-xN-based back-illuminated solar-blind photodetectors with external quantum efficiency of 89%,” Appl. Phys. Lett. 103(19), 191108 (2013). [CrossRef]
13. M. Fan, K. Liu, Z. Zhang, B. Li, X. Chen, D. Zhao, C. Shan, and D. Shen, “High-performance solar-blind ultraviolet photodetector based on mixed-phase ZnMgO thin film,” Appl. Phys. Lett. 105(1), 011117 (2014). [CrossRef]
14. C. Lin, Y. Lu, X. Yang, Y. Tian, C. Gao, J. Sun, L. Dong, F. Zhong, W. Hu, and C. Shan, “Diamond-based all-carbon photodetectors for solar-blind imaging,” Adv. Opt. Mater. 6, 1800068 (2018). [CrossRef]
15. J. Pearton S, J. Yang, P. H. Cary IV, F. Ren, J. Kim, J. Tadjer M, and A. Mastro M, “A review of Ga2O3 materials, processing, and devices,” Appl. Phys. Rev. 5(1), 011301 (2018). [CrossRef]
16. X. Chen, K. Liu, Z. Zhang, C. Wang, B. Li, H. Zhao, D. Zhao, and D. Shen, “Self-powered solar-blind photodetector with fast response based on Au/β-Ga2O3 nanowires array film Schottky junction,” ACS Appl. Mater. Interfaces 8(6), 4185–4191 (2016). [CrossRef]
17. M. Chen, B. Zhao, G. Hu, X. Fang, H. Wang, L. Wang, J. Luo, X. Han, X. Wang, C. Pan, and Z. Wang, “Piezo-phototronic effect modulated deep UV photodetector based on ZnO-Ga2O3 heterojuction microwire,” Adv. Funct. Mater. 28, 1706379 (2018). [CrossRef]
18. D. Guo, Y. Su, H. Shi, P. Li, N. Zhao, J. Ye, S. Wang, A. Liu, Z. Chen, C. Li, and W. Tang, “Self-powered ultraviolet photodetector with superhighphotoresponsivity (3.05 A/W) based on the GaN/Sn:Ga2O3 pn junction,” ACS Nano 12(12), 12827–12835 (2018). [CrossRef]
19. S. Han, X. Huang, M. Fang, W. Zhao, S. Xu, D. Zhu, W. Xu, M. Fang, W. Liu, P. Cao, and Y. Lua, “High-performance UV detectors based on room-temperature deposited amorphous Ga2O3 thin films by RF magnetron sputtering,” J. Mater. Chem. C 7(38), 11834–11844 (2019). [CrossRef]
20. L. Huang, Z. Hu, H. Zhang, Y. Xiong, S. Fan, C. Kong, W. Li, L. Ye, and H. Li, “A simple, repeatable and highly stable self-powered solar-blind photoelectrochemical-type photodetector using amorphous Ga2O3 films grown on 3D carbon fiber paper,” J. Mater. Chem. C 9(32), 10354–10360 (2021). [CrossRef]
21. H. Wong M, C. Lin, A. Kuramata, S. Yamakoshi, H. Murakami, Y. Kumagai, and M. Higashiwakil, “Acceptor doping of β-Ga2O3 by Mg and N ion implantations,” Appl. Phys. Lett. 113(10), 102103 (2018). [CrossRef]
22. R. Rao, M. Rao A, B. Xu, J. Dong, S. Sharma, and K. Sunkara M, “Raman scattering and its correlation with the [110] growth direction in gallium oxide nanowires,” J. Appl. Phys. 98(9), 094312 (2005). [CrossRef]
23. J. Zhang and F. Jiang, “Catalytic growth of Ga2O3 nanowires by physical evaporation and their photoluminescence properties,” Chem. Phys. 289(2-3), 243–249 (2003). [CrossRef]
24. X. Hou, H. Sun, S. Long, S. Tompa G, T. Salagaj, Y. Qin, Z. Zhang, P. Tan, S. Yu, and M. Liu, “Ultrahigh-performance solar-blind photodetector based on α-phase- dominated Ga2O3 film with record low dark current of 81 fA,” IEEE Electron Device Lett. 40(9), 1483–1486 (2019). [CrossRef]
25. S. Li, J. Yue, X. Ji, C. Lu, Z. Yan, P. Li, D. Guo, Z. Wu, and W. Tang, “Oxygen vacancies modulating the photodetector performances in ɛ-Ga2O3 thin films,” J. Mater. Chem. C 9(16), 5437–5444 (2021). [CrossRef]
26. S. Oh, K. Kim C, and J. Kim, “High responsivity β-Ga2O3 metal-semiconductor-metal solar-blind photodetectors with ultraviolet transparent graphene electrodes,” ACS Photonics 5(3), 1123–1128 (2018). [CrossRef]
27. Y. Chen, Y. Lu, Q. Liu, C. Lin, J. Guo, J. Zang, Y. Tian, and C. Shan, “Ga2O3 photodetector arrays for solar-blind imaging,” J. Mater. Chem. C 7(9), 2557–2562 (2019). [CrossRef]
28. C. Xie, X. Lu, Y. Liang, H. Chen, L. Wang, C. Wu, D. Wu, W. Yang, and L. Luo, “Patterned growth of β-Ga2O3 thin films for solar-blind deep-ultraviolet photodetectors array and optical imaging application,” J. Mater. Sci. Technol. 72, 189–196 (2021). [CrossRef]
29. W. Feng, X. Wang, J. Zhang, L. Wang, W. Zheng, P. Hu, W. Cao, and B. Yang, “Synthesis of two-dimensional β-Ga2O3 nanosheets for high-performance solar blind photodetectors,” J. Mater. Chem. C 2(17), 3254–3259 (2014). [CrossRef]
30. S. Li, D. Guo, P. Li, X. Wang, Y. Wang, Z. Yan, Z. Liu, Y. Zhi, Y. Huang, Z. Wu, and W. Tang, “Ultrasensitive, superhigh signal-to-noise ratio, self-powered solar-blind photodetector based on n-Ga2O3/p-CuSCN core–shell microwire heterojunction,” ACS Appl. Mater. Interfaces 11(38), 35105–35114 (2019). [CrossRef]
31. X. Pan, J. Zhang, H. Zhou, R. Liu, D. Wu, R. Wang, L. Shen, L. Tao, J. Zhang, and H. Wang, “Single-layer ZnO hollow hemispheres enable high-performance self-powered perovskite photodetector for optical communication,” Nano-Micro Lett. 13(1), 12 (2021). [CrossRef]
32. Y. Chen, Y. Lu, M. Liao, Y. Tian, Q. Liu, C. Gao, X. Yang, and C. Shan, “3D solar-blind Ga2O3 photodetector array realized via origami method,” Adv. Funct. Mater. 29, 1906040 (2019). [CrossRef]
33. L. Qian, Z. Wu, Y. Zhang, T. Lai P, X. Liu, and Y. Li, “Ultrahigh-responsivity, rapid-recovery, solar-blind photodetector based on highly nonstoichiometric amorphous gallium oxide,” ACS Photonics 4(9), 2203–2211 (2017). [CrossRef]
34. S. Cui, Z. Mei, Y. Zhang, H. Liang, and X. Du, “Room-temperature fabricated amorphous Ga2O3 high-response-speed solar-blind photodetector on rigid and flexible substrates,” Adv. Opt. Mater. 5, 1700454 (2017). [CrossRef]
35. Q. Wang, J. Chen, P. Huang, M. Li, Y. Lu, P. Homewood K, G. Chang, H. Chen, and Y. He, “Influence of growth temperature on the characteristics of β-Ga2O3 epitaxial films and related solar-blind photodetectors,” Appl. Surf. Sci. 489, 101–109 (2019). [CrossRef]
36. S. Pratiyush A, S. Krishnamoorthy, V. Solanke S, Z. Xia, R. Muralidharan, S. Rajan, and N. Nath D, “High responsivity in molecular beam epitaxy grown β-Ga2O3 metal semiconductor metal solar blind deep-UV photodetector,” Appl. Phys. Lett. 110(22), 221107 (2017). [CrossRef]
37. Y. Li, Y. Zhang D, R. Lin, Z. Zhang, W. Zheng, and F. Huang, “Graphene interdigital electrodes for improving sensitivity in a Ga2O3:Zn deep-ultraviolet photoconductive detector,” ACS Appl. Mater. Interfaces 11(1), 1013–1020 (2019). [CrossRef]
38. D. Patil-Chaudhari, M. Ombaba, Y. Oh J, H. Mao, H. Montgomery K, A. Lange, S. Mahajan, M. Woodall J, and S. Islam M, “Solar blind photodetectors enabled by nanotextured β-Ga2O3 films grown via oxidation of GaAs substrates,” IEEE Photonics J. 9(2), 1–7 (2017). [CrossRef]
39. G Qiao, Q Cai, M Ma, J Wang, X Chen, Y Xu, Z Shao, J Ye, and D Chen, “Nanoplasmonic enhanced high-performance metastable phase α-Ga2O3 solar-blind photodetector,” ACS Appl. Mater. Interfaces 11(43), 40283–40289 (2019). [CrossRef]
