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Article

High-Performance Nanoplasmonic Enhanced Indium Oxide—UV Photodetectors

1
Department of Physics, University of Puerto Rico, San Juan, PR 00936, USA
2
Department of Chemistry, Biochemistry, Physics, and Engineering, Indiana University of Pennsylvania, Indiana, PA 15705, USA
*
Authors to whom correspondence should be addressed.
Crystals 2023, 13(4), 689; https://doi.org/10.3390/cryst13040689
Submission received: 23 March 2023 / Revised: 12 April 2023 / Accepted: 14 April 2023 / Published: 17 April 2023
(This article belongs to the Special Issue 1D and 2D Nanomaterials for Sensor Applications)

Abstract

:
In this paper, high-performance UV photodetectors have been demonstrated based on indium oxide (In2O3) thin films of approximately 1.5–2 μm thick, synthesized by a simple and quick plasma sputtering deposition approach. After the deposition, the thin-film surface was treated with 4–5 nm-sized platinum (Pt) nanoparticles. Then, titanium metal electrodes were deposited onto the sample surface to form a metal–semiconductor–metal (MSM) photodetector of 50 mm2 in size. Raman scattering spectroscopy and scanning electron microscope (SEM) were used to study the crystal structure of the synthesized In2O3 film. The nanoplasmonic enhanced In2O3-based UV photodetectors were characterized by various UV wavelengths at different radiation intensities and temperatures. A high responsivity of up to 18 A/W was obtained at 300 nm wavelength when operating at 180 °C. In addition, the fabricated prototypes show a thermally stable baseline and excellent repeatability to a wide range of UV lights with low illumination intensity when operating at such a high temperature.

1. Introduction

Indium oxide (In2O3) has received much attention in multidisciplinary device applications such as flat-panel displays, light-emitting diodes (LEDs), and solar cells. Moreover, in recent years, indium oxide nanomaterials with different morphologies (nanoparticles, nanoflowers, nanosheets, nanowires, etc.) [1,2] have been found to be promising candidates for gas sensors [3,4,5]. On the other hand, indium oxide is a desirable material for developing smart, flexible, and wearable optoelectronics and multifunctional sensors in the field of environmental indicators [6], owing to its wide band gap (with reported values ranging from 2.7 to 3.7 eV) [7], optical transparency, thermal and chemical resistance, flexibility and stretchability, ease of manufacturing and low fabrication cost. Hence, UV photodetectors (PDs) based on In2O3 nanostructures, such as nanowires [8,9,10], quantum dots [11], nanosheets [12], and nanoparticles [13], have been explored, which demonstrates that In2O3 is a candidate for developing UV PDs. However, there are neither reports on the UV photodetector based on In2O3 thin films, nor studies on PD performance comparison at different temperatures.
Recently, surface functionalization with noble metal nanoparticles (NPs, e.g., Au and Ag) was effectively used to improve ZnO [14], GaN [15] and UNCD [16] UV photodetector performances. The effects of different metals such as Pt, Al and Ag as well as nanoparticle size have been discussed in our previous publications [16,17,18,19]. The nanoplasmonic resonance in metal nanoparticles causes the strong absorption and scattering of incident light. As a result, the photodetector showed high responsivity, which is defined as the ratio of generated photocurrent and incident optical power. Although the surfaced functionalization of noble metal nanoparticles was demonstrated in indium oxide-based gas sensors [20], to date, no papers have been published on surface functionalized In2O3 UV photodetectors with noble metal nanoparticles.
In the present work, we demonstrated a high-performance In2O3 UV photodetector with Pt nanoparticle surface functionalization. Pt nanoparticles were chosen due to their localized plasmon resonance featured in the UV region [21]. Very high responsivities have been obtained both at room temperature and an elevated temperature, which is much better than that of UV photodetectors with MSM (metal–semiconductor–metal) structures based on SiC [22], diamond [23], and oxides [24] that can operate at high temperatures. The fabricated prototypes show a thermally stable baseline and excellent repeatability to a wide range of UV lights with low illumination intensity.

2. Materials and Methods

Compared to metal–organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) techniques, sputtering has features of a high deposition rate, low cost, acceptable quality of thin films, and capability to deposit on large-area substrates. Owing to these advantages and their flexibility in the control of composition and microstructure, magnetron sputtering is widely employed for the synthesis of various thin films. The In2O3 thin films used in this study were grown on Si (100) substrates under deposition durations of 15 min using a homemade RF reactive magnetron sputtering system [25] with a power of 200 W. The substrates were cleaned in acetone and methanol with ultrasonic vibration and then dried with blowing dry nitrogen gas before deposition. The target for the growth of In2O3 films was sintered In2O3 (99.9%), 2 -inch in diameter. The distance between the target and substrate was approximately 7–8 cm. All the films were deposited at room temperature and the obtained thickness of the sample was approximately 1.5–2.0 µm measured using a stylus surface profiler (DektakXT, BRUKER, Billerica, MA). After deposition, the samples were annealed at 400, 600 and 800 °C for 2 h, respectively. The base pressure of the chamber was on the order of 10−6 Torr and the working pressure with argon gas was maintained at approximately 8–10 mTorr. To enhance the responsivity of the In2O3 thin–film material to UV radiation, the samples were functionalized using platinum (Pt) nanoparticles before photodetector fabrication. The surface treatments with Pt nanoparticles lasted for 1–2 s by using a 200 W RF magnetron sputtering deposition technique.

3. Results and Discussions

SEM was utilized to generate high-resolution photographs of surface morphology, along with a Raman spectrometer enabling a deeper insight into structural information. Figure 1a–c show SEM images of three In2O3 samples after annealing at 400, 600 and 800 °C, respectively, for 2 h. The surfaces of the obtained samples are flat but many particles on the surface were clearly visible. Following an increase in the temperature on annealing, the sizes of these particles increased from the sub-micrometer range to approximately 1 micrometer. A tentative interpretation is that melting and dissociation of partial In2O3 thin films into droplets on the surfaces of the samples during annealing at very high temperatures results in a rough/coarse surface.
Generally, the coarse surface of sample-based devices would be seriously affected by the surrounding environment such as humidity or dust. Therefore, in the following part, the focus would be on the first sample (as shown in Figure 1a) annealed at 400 °C with better surface quality. As an n-type semiconductor, different preparation methods and conditions influence the crystalline structures of In2O3 synthesized, such as cubic or rhombohedral, although both have the same band gap energy. The body-centered cubic (bcc) In2O3 with lattice parameter a = 1.011 nm is the most stable structure that is preferred for electronic [26] applications due to its high conductivity.
The In2O3 films prepared for this study were characterized by room-temperature Raman spectroscopy. An Ar+ ion laser (Model 95, Lexcel Laser Inc., Fremont, CA) with an excitation wavelength of 514 nm was used along with a triple-grating monochromator to measure the Raman spectra. The ~2 mW laser beam, after passing through an 80× Olympus microscope objective, was focused onto the sample surface with a spot size of 3~4 μm in diameter, corresponding to a laser power density of approximately 2 × 104 W/cm2. It was noticed that at this power density, no obvious surface morphology change in the In2O3 samples was observed because of the annealing effect caused by the laser beam with an accumulation time of 30 s required by the Raman measurement. Figure 2 shows Raman spectra of In2O3 film deposited on Si(100) substrate before and after the surface treatment with platinum nanoparticles. As displayed in Figure 2, the strongest peak at approximately 521 cm−1 is from the Si substrate. The spectra from In2O3 are dominated by the optical phonon lines at 132, 307, 366, 495, and 627 cm−1, corresponding to bcc In2O3. The narrow spectral lines at 132 and 307 cm−1 confirmed the good crystalline quality of the bcc In2O3 films.
The fast fabrication process of the In2O3 thin-film-based photodetector is shown in Figure 3a. After the In2O3 thin film was deposited on Si(100) substrate, the sample surface was decorated with Pt nanoparticles. Then, a mask made of a metal wire of 400 μm in diameter was placed over the top surface of the In2O3 sample, followed by a 2-min direct coating of Ti metal electrodes of a thickness of 0.5–1 μm. The fabricated In2O3 UV photodetector was finally annealed at 200 °C for 60 min in the same vacuum chamber. Figure 3b shows the edge between the Ti electrode (grey) and In2O3 sensing material (black). The MSM geometry of the photodetector used in this investigation was similar to our previous boron nitride-based and SiC-based UV photodetectors [22,27] except for the In2O3 sensing layer. The gap formed by this simple and quick fabrication process was 400 μm between a pair of electrical electrodes, leading to a totally exposed surface area of 15 mm2, although smaller gaps can be obtained with a more tedious lithography process.
Once the process flow of the MSM UV photodetector was completed, the prototypic UV photodetector was tested for its I–V graph and the photon-induced electrical current Iph when the sensing material was exposed to UV radiation. As shown in Figure 3c, the prototype is connected in series with a precise resistor Rprecise, a switch, and an Agilent voltage source power supply Vo. The voltage variations during the characterization across the precise resistor were monitored with a HEWLETT 34,401 electrical multimeter controlled by the LabVIEW program. To control the operating temperature of the tested prototype, a thermocouple and tungsten filament were deployed. The error of the measurements was approximately 5%.
The UV sensing mechanism of the In2O3 photodetector can be understood as a photoelectric phenomenon. As an n-type semiconductor, the conductivity of the In2O3 photodetector is largely due to the depletion region formed when there is no UV illumination because oxygen molecules trap free electrons to be ionized and chemisorbed on the surface. With UV radiation of photon energy slightly equal to or greater than the energy band gap of In2O3, the photoelectrically generated hole carriers recombine negatively charged adsorbed oxygen ions on the surface and discharge oxygen molecules that reduce the depletion region and increase the conductivity of the In2O3 sensing layer. Further illumination of UV light will generate more electron–hole pairs in the conduction and valence bands, which decreases the resistance significantly.
Figure 4a exhibits the four I–V graphs, i.e., the measured dark current as a function of the applied bias voltage when the prototype operates at room temperature (RT, 23 °C), 40 °C, 80 °C, and 120 °C, respectively, when the bias increases from zero to a maximum of 11 V. The linear relationship indicates a good ohmic contact formed between the electrode and the semiconductor except for a slightly curved I–V graph at room temperature. At room temperature, the unpaired electrons are collected at the anode under bias, which leads to a decrease in the width of the depletion layer. Therefore, an increase in conductivity occurs with an increase in the bias voltage. As a comparison, at room temperature, the dark current is approximately 28 μA at 4 V bias and 87 μA at 11 V.
The increase in dark current at higher temperatures is directly attributed to material properties. An increase in the operating temperature up to 40 and 80 °C results in an increase in the dark current to 42 μA and 80 μA at 4 V bias, respectively. With the increase in operating temperature, a lower resistance takes place with the departure of the chemisorbed oxygen molecules from the surface. As shown in Figure 4a, when biased at 4 V, the dark currents are 28, 43, and 80 μA for room temperature, 40 °C and 80 °C operation, respectively. When the temperature is high enough and the sample surface is already maintained in a chemisorbed oxygen molecule free or rather a dynamic equilibrium state, as indicated by the I–V graphs at 80 °C and 120 °C in Figure 4a, further increase in the operating temperature does not boost the current. Similarly, as revealed in Figure 4b, the resistance of the device decreases with the increase in operating temperature. After the operating temperature reaches 80 °C, the resistance remains the same and no longer declines with the temperature rise.
To verify the authenticity of the photocurrent, the fabricated prototype was tested with UV light illuminations at different wavelengths for a period of 4 min and 50% duty, as shown in Figure 5. The device was operating at room temperature when the incident UV light intensity was 2 mW/cm2 on the detector surface, which was controlled by varying the distance between the UV light source and the detector surface. As shown in Figure 5, the photocurrent rises and falls as the light is turned on and off when biased at 3.5 V. Besides, the device also displays good stability during the illumination cycle test. Under 250 nm, 300 nm, and 350 nm UV light illumination, the induced photocurrent is 0.39 mA, 0.48 mA, and 0.78 mA, respectively. At a longer wavelength, although the photocurrent is greater, the In2O3 prototype takes a longer time to respond. As indicated in Figure 5a,b, the measured photocurrent builds up quicker under 250 nm and 300 nm UV light, compared to 350 nm UV light illumination. On the other hand, noise under 250 nm UV light is greater than that under 300 nm and 350 nm UV light, since noise is greater at a short wavelength when the light intensity is fixed.
Figure 6 shows the typical dependence of the photocurrent on UV light intensity under a bias of 3.5 V at room temperature. When the detector was exposed with a period of 4 min between the “switch-on” and “switch-off” to a 250 nm UV light at an intensity of 0.013 mW/cm2, a well-defined light-induced photocurrent was obtainable with sharp edges. When the UV source was switched off, the photocurrent responded sharply down and then gradually decayed to zero. As expected, with the enhancement of illumination intensity, more electron-hole pairs are excited that contribute to the enriched photocurrent. As shown in Figure 6a–c, when exposed with the light intensities of 0.013, 0.17, and 2 mW/cm2, the photocurrent measured are 0.10, 0.16 and 0.38 mA, respectively.
The photodetector’s responsivity, Rλ, is defined as
R λ = I p h p l i g h t ,
where Iph is the maximal photocurrent from the detector, and Plight is the total incident light power on the surface of the detector. It can be estimated based on the experimental data. Since the exposed surface area of the detector is 15 mm2, 250 nm light power on the surface of the detector at 13 μW/cm2 intensity is approximately 1.95 μW, leading to a responsivity of 51 A/W at the bias of 3.5 V. When the intensities were increased to 0.17 mW/cm2, and 2 mW/cm2, the responsivity dropped to 6.3 A/W and 1.3 A/W, respectively. The reduction in responsivity under greater UV light intensity could be caused by the saturation of the sensing layer.
The external quantum efficiency (EQE), η, can be expressed by
η   =   R λ h C λ q
where h is Planck’s constant, c the speed of light, q the electron charge, and λ the incident wavelength. A responsivity of 51 A/W at 250 nm corresponds to a quantum efficiency of 25.296% when operating at room temperature under an illumination intensity of 13 μW/cm2 and a bias voltage of 3.5 V. We can also estimate the special detectivity D* at this wavelength according to the following equation:
D *   =   R λ A 2 q I d   ,
where Id = 0.025 mA is the dark current at room temperature (Figure 4a). The calculated special detectivity is 7.0 × 1012 Jones at a power density of 13 μW/cm2.
To find the photodetector’s response at different UV wavelengths, 300 nm UV light was also used with different intensities ranging from 0.013, 0.02, 0.17 to 2 mW/cm2, as shown in Figure 6d–g, corresponding to photocurrents of 0.1, 0.17, 0.24 and 0.46 mA, respectively. Higher photocurrents were obtained, compared to 250 nm UV light at the same intensities. The rise time and recovery time, on the other hand, were slightly longer than those under 250 nm wavelength UV light. Because of the MSM geometry, charge carriers generated close to the surface and top region can contribute to a fast rise time. While charge carriers generated further away from the surface must take extra time to diffuse to the electrodes, leading to a longer rise time. We believe that at 300 nm wavelength, the photocurrent of the prototype was dominated by the photo-generated charge carriers inside the layer rather than that from the surface, which travels a longer average distance, hence a longer rise time, to generate the current. Our observations also indicate that the absorption of 250 nm could be greater than that of 300 nm UV light. However, its lower responsivity at relatively greater illumination light intensity could be caused by the possible saturation due to its higher absorption. A trade-off should be made between the photocurrent and response time as the In2O3 layer thickness is optimized. The response of a device to different light illumination may also rely on the bandgap width or cross-section parameter of the active layer.
Since the temperature effect of In2O3 UV photodetectors has not been studied by other groups, it is interesting to see how an In2O3 UV photodetector behaves at different operating temperatures. Therefore, additional experiments have also been carried out and the photocurrents responding to 250 nm and 300 nm UV illumination when operated at room temperature, 180 °C and 300 °C are displayed in Figure 7. Under 250 nm UV light, with the increase in operating temperature from room temperature to 180 °C, the yielded photocurrent increases from 0.2 mA to 0.6 mA. However, the contribution of thermal noise to the obtained photocurrent increases too, as shown in Figure 7a–c. When the operating temperature was further raised to 300 °C, the photocurrent was completely buried under noise.
As shown in Figure 7d–f, under 300 nm UV light of an intensity of 0.17 mW/cm2, following the increase in temperature from 23 °C (RT) to 180 °C and then to 300 °C, the photocurrent was first increased from 0.28 mA to 0.47 mA and then decreased to 0.19 mA, giving a responsivity of 18 A/W at 180 °C and 7.3 A/W at 300 °C. The trend observed is similar to what was discovered with the In2O3-based oxygen sensors [28,29]. It is believed that with the temperature increase, apart from the resistance decrease due to the departure of adsorbed oxygen on the In2O3 surface, it is possible that the charge-carrier concentration increases, and the Debye length decreases and thus the sensitivity decreases [16].
The device also showed a faster response time and recovery time, and other good features such as excellent stability and repeatability, and a highly stable baseline when operating at both 180 and 300 °C. Upon receiving the UV light, the photocurrent reached its peak quickly and then dropped to zero gradually after the light source was switched off. The rise time, τr, which is defined as the interval from 10% to 90% of Imax, and fall time, τf, which is defined as the interval from 90% to 10% of Imax, are τr = 0.57 s and τf = 1.4 s, respectively, when the device is irradiated with UV pulses. The short rise time is attributed to the Pt nanoparticle decoration and the low capacitance of the MSM geometry, although its responsivity is limited due to the small effective absorbing area caused by the metallization of the electrodes.
In fact, the noble metal nanoparticles deposited on a metal oxide semiconductor surface act as electron-hole separators to promote the interfacial charge-transfer kinetics between the metal and semiconductor as reported in [14]. For example, the Ag-nanoparticle-decorated ZnO nanowire-based UV photodetector effectively eliminated the common persistent photoconductivity effect, leading to a significant decrease in the rise time as well as the dark current. However, the relatively long fall time is possible owing to the well-known persistent photoconductivity (PPC) effect in metal oxide nanostructure-based UV photodetectors, governed by the presence of numerous trapping states at crystal defects and the depth of the trap that prevent the photogenerated minority carriers from recombination and prolong the recovery time. As a comparison, Table 1 outlines the reported performance parameters of UV photodetectors operating at elevated temperatures.

4. Conclusions

In2O3 thin films were synthesized on Si substrates using the RF sputtering technique, followed by the surface decoration of Pt nanoparticles. The Raman spectroscopy measurements confirmed that the thin films consisted of crystalline cubic In2O3. Finally, an MSM UV photodetector was fabricated using a simple and low-cost approach. The synthesis of a thin-film layer used for the UV photodetector eliminated the tight control needed for a nanostructure counterpart. Furthermore, there was no requirement for an expansive photolithography process in the device fabrication. A high responsivity to a wide range of UV light from 250 to 350 nm was demonstrated for the fabricated photodetector, as well as good stability and repeatability. When operated with a 3.5 V bias at room temperature, a responsivity of 50 A/W was achieved at 250 nm wavelength. Following a slight increase in the operating temperature, the fabricated photodetector runs well with improved responsivity, stability, and repeatability, as well as a faster rise time and fall time. However, a further increase in operating temperature would eventually lead to high thermal noise that dominates the output. The obtained experimental data indicated that at under 300 nm radiation, the best performance was achieved at 180 °C although the device was still working properly at temperatures up to 300 °C. This characteristic is much better than that of UV photodetectors based on other materials that were reported to operate at high temperatures but were generally limited to less than 150 °C. This experimental investigation suggests that the simple approach described provides quick fabrication of high-performance UV photodetectors, which could possibly handle a high operating temperature of up to 300 °C.

Author Contributions

Designing and performing the experiments, as well as analyzing the data and writing this manuscript, E.Y.L., A.F.Z. and P.X.F. All authors have read and agreed to the published version of the manuscript.

Funding

NSF-CREST Center for Innovation, Research and Education in Environmental Nanotechnology (CIRE2N), grant HRD-1736093.

Data Availability Statement

Not applicable.

Acknowledgments

This work was financially supported by the NSF-CREST Center for Innovation, Research and Education in Environmental Nanotechnology (CIRE2N), grant HRD-1736093. A.F.Z. acknowledges the receipt of an IUP USRC research grant award.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. SEM images of In2O3 samples annealed at (a) 400 °C, (b) 600 °C, and (c) 800 °C, respectively, for 2 h.
Figure 1. SEM images of In2O3 samples annealed at (a) 400 °C, (b) 600 °C, and (c) 800 °C, respectively, for 2 h.
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Figure 2. Raman scattering spectra of In2O3 thin film prepared on Si substrate (a) before and (b) after Pt treatment. The large peak at 521 cm−1 from the Si substrate is labeled as “S”.
Figure 2. Raman scattering spectra of In2O3 thin film prepared on Si substrate (a) before and (b) after Pt treatment. The large peak at 521 cm−1 from the Si substrate is labeled as “S”.
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Figure 3. (a) Schematic diagram of the fabrication of the In2O3-based UV photodetector. (b) SEM image of the edge between the Ti electrode (grey) and sensing material (black) of the prototype. (c) Experimental setup for measuring electric properties and light responsivity of the UV photodetector.
Figure 3. (a) Schematic diagram of the fabrication of the In2O3-based UV photodetector. (b) SEM image of the edge between the Ti electrode (grey) and sensing material (black) of the prototype. (c) Experimental setup for measuring electric properties and light responsivity of the UV photodetector.
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Figure 4. (a) Electrical current as a function of bias voltage at four different temperatures: room temperature (RT, 23 °C), 40 °C, 80 °C, and 120 °C. Inset: the schematic of the photodetector. (b) The temperature effect on the electrical resistance property of the In2O3 prototype.
Figure 4. (a) Electrical current as a function of bias voltage at four different temperatures: room temperature (RT, 23 °C), 40 °C, 80 °C, and 120 °C. Inset: the schematic of the photodetector. (b) The temperature effect on the electrical resistance property of the In2O3 prototype.
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Figure 5. Photocurrent responding to 2 mW/cm2 UV signals of a period of 4 min and a 50% duty cycle at (a) 250 nm, (b) 300 nm, and (c) 350 nm, respectively, when operating at room temperature and 3.5 V bias voltage.
Figure 5. Photocurrent responding to 2 mW/cm2 UV signals of a period of 4 min and a 50% duty cycle at (a) 250 nm, (b) 300 nm, and (c) 350 nm, respectively, when operating at room temperature and 3.5 V bias voltage.
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Figure 6. The measured photocurrents when illuminated with 250 nm of (a) 0.013 mW/cm2, (b) 0.17 mW/cm2, (c) 2 mW/cm2, and when illuminated with 300 nm of (d) 0.013 mW/cm2, (e) 0.02 mW/cm2, (f) 0.17 mW/cm2 and (g) 2 mW/cm2, respectively. The device was operated at room temperature and biased at 3.5 V.
Figure 6. The measured photocurrents when illuminated with 250 nm of (a) 0.013 mW/cm2, (b) 0.17 mW/cm2, (c) 2 mW/cm2, and when illuminated with 300 nm of (d) 0.013 mW/cm2, (e) 0.02 mW/cm2, (f) 0.17 mW/cm2 and (g) 2 mW/cm2, respectively. The device was operated at room temperature and biased at 3.5 V.
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Figure 7. Photocurrents under UV light of 250 nm and 300 nm at an intensity of 0.17 mW/cm2 with a period of 4 min at 50% duty cycle when operated at (a,d) room temperature (RT), (b,e) 180 °C, and (c,f) 300 °C. The bias voltage is 3.5 V.
Figure 7. Photocurrents under UV light of 250 nm and 300 nm at an intensity of 0.17 mW/cm2 with a period of 4 min at 50% duty cycle when operated at (a,d) room temperature (RT), (b,e) 180 °C, and (c,f) 300 °C. The bias voltage is 3.5 V.
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Table 1. Comparison of the key device performance of the reported UV photodetectors.
Table 1. Comparison of the key device performance of the reported UV photodetectors.
MaterialPeak λ
(nm)
Responsivity (A/W)Bias Voltage (V)Response TimeTemperature Tested (°C)Ref
SiC 2500.11018 s180[22]
Diamond 3502.00< 1 sRT[23]
TiO2 2200.23020 μsRT[24]
In2O3 quantum dots290705-RT[11]
In2O3 nanosheets2540.172--RT[12]
In2O3 nanoparticles3401120500 sRT[13]
In2O3 film30018 3.50.57 s180This work
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Li, E.Y.; Zhou, A.F.; Feng, P.X. High-Performance Nanoplasmonic Enhanced Indium Oxide—UV Photodetectors. Crystals 2023, 13, 689. https://doi.org/10.3390/cryst13040689

AMA Style

Li EY, Zhou AF, Feng PX. High-Performance Nanoplasmonic Enhanced Indium Oxide—UV Photodetectors. Crystals. 2023; 13(4):689. https://doi.org/10.3390/cryst13040689

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Li, Eric Y., Andrew F. Zhou, and Peter X. Feng. 2023. "High-Performance Nanoplasmonic Enhanced Indium Oxide—UV Photodetectors" Crystals 13, no. 4: 689. https://doi.org/10.3390/cryst13040689

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