Search

Sensitive high‐energy photon detection from UV to X‐ray and high‐resolution array imaging are critical for medical diagnosis, space exploration, and scientific research. The key challenges for high‐performance photodetector and imaging arrays are the effective material and device design strategies for the miniaturization and integration of the device. Here, photon‐controlled diodes (i.e., the detector has rectifying characteristics only under light irradiation) are proposed for high‐resolution and anti‐crosstalk array imaging applications without integrating the switching element. Based on ultra‐wide bandgap semiconductor Ga2O3, the sensitive DUV/X‐ray photon‐controlled diodes are realized by the design of high‐resistance Ga2O3 film and high‐barrier contact. The device exhibits remarkable detection performance, including high photo‐responsivity (168 A W−1) and specific detectivity (1.45 × 1015 Jones) under DUV illumination, as well as a high sensitivity (1.23 × 105 µC Gyair−1 cm−2) under X‐ray light. Moreover, the low dark current and excellent rectification characteristics are obtained. Furthermore, its potential for high‐density and anti‐crosstalk array imaging applications is verified. These results not only bring forth new insights in the implementation of high‐performance DUV/X‐ray photodetector, but also pave a feasible way to realize high pixel density detector array through the simplified fabrication process for high‐resolution imaging applications. [ABSTRACT FROM AUTHOR]

Gallium oxide (Ga2O3), with an ultrawide bandgap corresponding to the deep ultraviolet (DUV) range, has attracted significant attention in optical filter‐free photodetectors. In practical terms, DUV photodetectors employed in extreme conditions, for example, flame detection and space exploration, face the challenges of performance degradation caused by high/low‐temperature transformation. Here, DUV photodetectors are tailored with high durability and stability by one‐step‐grown β‐Ga2O3 films via pulsed laser deposition. A high‐oxygen‐pressure scheme effectively addresses the issue of film‐free deposition at specifically high temperatures, facilitating the formation of polycrystalline high‐resistivity β‐Ga2O3 films. As a result, the devices exhibit outstanding performance, including a low dark current (4.4 pA @30 V), high photoresponsivity (147.36 A W−1), and fast response time (3.1/22.6 ms). Additionally, the photoresponse performance shows minimal degradation at high temperatures up to 300 °C and even improves at low temperatures down to −100 °C, ranking it among the most robust DUV photodetectors. The mechanism of photoresponse, involving the exciton formation, bandgap evolution, carrier‐phonon scatter, etc., is also elucidated in a wide temperature range. This work provides an efficient solution for developing robust Ga2O3 DUV photodetectors with excellent performance for extreme‐condition applications. [ABSTRACT FROM AUTHOR]

Ga2O3 photodetectors with demonstrated high sensitivity provide a potential subversive scheme for solar‐blind photodetection. However, the planar structure and the relatively slow response speed of the device have restricted the integration and application of Ga2O3 photodetectors. Herein, a narrow SiO2 barrier layer is introduced on the commercial SiC substrate, and a vertical photodetector is realized based on β‐Ga2O3/SiO2/SiC heterostructure with controllable tunneling effect by tailoring the band structure at the interface. The developed device exhibits unconventional rectification characteristics and photoresponse performance in different biasing modes owing to the controllable tunneling effect at the interface. In particular, the photodetector achieves a high responsivity (186.8 A W−1) under solar‐blind illumination at reverse bias, while exhibiting obvious advantages in dark current (3 pA), photo‐to‐dark current ratio (8.8 × 106), linear dynamic range (138.8 dB), and specific detectivity (1.4 × 1015 Jones) at forward bias. The photodetector also demonstrates excellent photoresponse stability after 6 months in air without encapsulation. In addition, an alternating biasing strategy, inspired by its bidirectional operability, is proposed to suppress the persistent photoconductivity effect and increase the decay speed by 1.23 × 105 times. This work provides a referable strategy for the further development of high‐performance Ga2O3‐based photoelectronics. [ABSTRACT FROM AUTHOR]

High deep‐ultraviolet (DUV) sensitivity and excellent flexibility of ultrathin gallium oxide (Ga2O3) film with an ultrawide bandgap endow its extreme propensity in flexible DUV photodetector especially for space exploration and wearable electronics. However, an efficient strategy with high throughput and low cost is highly deficient to realize flexible and robust Ga2O3 DUV photodetectors to face potential harsh environments. In this work, flexible and heat‐resistant Ga2O3 DUV photodetectors based on optimized inkjet printing with environmental‐friendly aqueous solvent are demonstrated. The dynamic evolution from Ga(NO3)3 precursor to crystalline Ga2O3 film has been explicitly uncovered. Photodetectors based on printed ultrathin Ga2O3 films on rigid substrate exhibit outstanding performance, including high photo‐to‐dark current ratio about 106, considerable responsivity of 1.3 A W−1, superior detectivity of 1.46 × 1014 Jones, and fast decay time of 0.026 s under 254 nm illumination. In addition, flexible devices on mica substrate not only retain outstanding photoelectrical performance, but also demonstrate excellent mechanical flexibility and thermal stability. Moreover, benefiting from the uniformity of the pixels by high‐throughput inkjet printing, the Ga2O3 DUV photodetector array presents excellent sharp‐imaging capability. This work provides a feasible strategy for printable, flexible, and harsh‐environment‐resistant Ga2O3 DUV photodetectors toward space exploration and wearable electronics. [ABSTRACT FROM AUTHOR]

High tunability of photoresponse characteristics under work conditions is desired for a single solar-blind photodetector to be applied in multifarious fields. Three-terminal metal–oxide–semiconductor field-effect phototransistors have shown excellent controllability of performance, but the hysteresis issue impedes their stable operation. In this work, the metal–semiconductor field-effect phototransistor based on the exfoliated Ga2O3 microflake and graphene thin film is demonstrated. The high-quality quasi-van der Waals interface between Ga2O3 and graphene eliminates the hysteresis issue and generates a subthreshold swing as low as 69.4 mV/dec. By regulating gate voltage (Vg), the dominated mechanism of photocurrent generation in the device can be tuned continuously from the fast photoconduction effect to photogating effect with high photogain. Accordingly, the responsivity, dark current, detectivity, rejection ratio, and decay time of the device can be well adjusted by the Vg. At Vg = −1 V and a source to drain voltage of 2 V, the device shows excellent performance with a responsivity of 2.82 × 103 A/W, a rejection ratio of 5.88 × 105, and a detectivity of 2.67 × 1015 Jones under 254 nm illumination. This work shows the possibility of realizing highly tunable solar-blind photodetectors to meet the requirements for different application fields by introducing gate voltage modulation. [ABSTRACT FROM AUTHOR]

The Ga2O3 solar-blind photodetectors (SBPDs) face the tradeoff between power consumption ($P_{\text {C}}$) and photoresponse performance. Here, an ultrasensitive two-terminal photodetector based on $\boldsymbol {\beta }$ -Ga2O3 microflake with extremely-low working voltage and ${P}_{\text {C}}$ was achieved. At a working voltage of 2 V and ${P}_{\text {C}}$ of 10 fW, the Ga2O3 SBPD exhibits superexcellent photodetection performance, including a responsivity (${R}$) of ${2.3}\,\,\times \,\,{10}^{{5}}\text{A}$ /W, a detectivity (${D}^{ \boldsymbol {\ast }}$) of ${3.5}\,\,\times \,\,{10}^{{18}}$ Jones, a photo-to-dark-current ratio (PDCR) of ${3.2}\,\,\times \,\,{10}^{{8}}$ , and an ultra-low dark current (${I}_{\text {dark}}$) of 5 fA. Strikingly, the device keeps satisfactory performance at ultralow working voltage of 0.01 V, including a ${P}_{\text {C}}$ of 0.05 fW, a ${R}$ of ${2.4}\,\,\times \,\,{10}^{{3}}$ A/W, a ${D}^{ \boldsymbol {\ast }}$ of ${5.6}\,\,\times \,\,{10}^{{16}}$ Jones, and a PDCR of ${3.4}\,\,\times \,\,{10}^{{6}}$. The superior solar-blind sensitivity makes it the most excellent Ga2O3 detector towards high-performance and low- $P_{\text {C}}$ SBPD applications. [ABSTRACT FROM AUTHOR]

Self‐powered solar‐blind photodiodes with convenient operation, easy fabrication, and weak‐light sensitivity, are highly desired in environmental monitoring and deep space exploration. Ga2O3 with its bandgap directly corresponding to solar‐blind waveband is a promising candidate material for solar‐blind photodetection. However, ever‐reported self‐powered Ga2O3 photodiodes suffer unsatisfactory photoresponse performance, owing to unideal interface and electrode transmittance. Here, Ag nanowire (AgNW) networks with excellent solar‐blind ultraviolet transmittance are introduced to form self‐powered AgNW–Ga2O3 photodiodes with sharp Schottky interfaces. The tradeoff between solar‐blind ultraviolet transmittance and carrier‐collection ability of the sparse AgNW network is systematically studied and the AgNW density is optimized for the best photoresponse. Expansion of depletion region outwards the AgNW–Ga2O3 contact and the field crowding effect facilitate the high photoresponse. As a result, the champion AgNW–Ga2O3 Schottky photodiode exhibits excellent sensitivity for weak‐light detection, including considerable responsivity of 14.8 mA W–1, ultrahigh photo‐to‐dark‐current ratio above 1.2 × 105, high rejection ratio (R254 nm/R365 nm) of 2.6 × 103, and fast response speed (rise/decay time of 20/24 ms) under self‐powered mode. Balancing the transmittance and carrier‐collection ability of elaborate electrode provides an alternative strategy to achieve high‐performance self‐powered Ga2O3 photodetectors for future weak‐light‐sensitive optoelectronic systems. [ABSTRACT FROM AUTHOR]

Light detection in the deep-ultraviolet (DUV) solar-blind waveband has attracted interest due to its critical applications, especially in safety and space detection. A DUV photodetector based on wide-bandgap semiconductors provides a subversive scheme to simplify the currently mature DUV detection system. As an ultra-wide-bandgap (4.4–5.3 eV) semiconductor directly corresponding to the DUV solar-blind waveband, Ga2O3 has an important strategic position in the prospective layout of semiconductor technology owing to its intrinsic characteristics of high breakdown electric field, excellent tolerance of high/low temperature, high resistance to radiation, and rich material systems. As the only native substrate that can be fabricated from melt-grown bulk single crystals, β-Ga2O3 has attracted a lot of attention both in power-electronic and photo-electronic devices. In addition, other metastable phases (e.g. α, ϵ, γ) of Ga2O3 have attracted great interest due to their unique properties. In this work, we discuss the advances in achieving bulk and film Ga2O3 materials with different crystal phases. In addition, the latest achievements with polymorphous Ga2O3-based solar-blind photodetectors (SBPDs) and the methods to enhance their performance, including doping, annealing, and transparent electrodes, are also discussed. Furthermore, as the most desirable application, DUV imaging technologies based on Ga2O3 SBPDs are systematically summarized. Finally, conclusions regarding recent advances in Ga2O3 SBPDs, remaining challenges, and prospects are presented and discussed. [ABSTRACT FROM AUTHOR]

β- Ga 2 O 3 solar-blind photodetector (SBPD) promises great potential applications in both industrial and scientific fields while it urgently needs performance optimization. Herein, the unique bottom-up Zn diffusion doping engineering was applied to fabricate an ultrahigh-performance β- Ga 2 O 3 planar MSM SBPD. High-quality β- Ga 2 O 3 film was grown by MOCVD heteroepitaxy technology on the cost-effective ZnGa 2 O 4 substrate, and the high-temperature growth process successfully realized the moderate diffusion Zn doping from the substrate to the film. This low-cost one-step doping not only reduces the dark current of the device to 635 fA at 20 V, which is 103 times lower than the β- Ga 2 O 3 film SBPD grown on a c-sapphire substrate under the same conditions, but also maintains the excellent crystal quality of the MOCVD grown film, thus brings the comprehensive performance of the device exceeding most reported β- Ga 2 O 3 SBPDs. The device exhibits a high photo-to-dark-current ratio of 1.18 × 107, high responsivity of 72.35 A/W, considerable rejection ratio (R 254 nm / R 365 nm) of 107, and extremely fast decay time of 8 ms under 254 nm illumination at 20 V. This work provides novel strategies of β- Ga 2 O 3 film optimization for the future development of high-performance photodetectors. • A high-quality β -Ga 2 O 3 film is grown by MOCVD on the low-cost ZnGa 2 O 4 substrate, while the unique bottom-up Zn diffusion doping engineering is applied, which obviously reduces the dark current of the MSM solar-blind photodetector (SBPD) based on the film. • The SBPD based on the film has a high I photo /I dark ratio of 1.18 × 107, considerable rejection ratio (R 254 nm/R 365 nm) of 107 and fast response. [ABSTRACT FROM AUTHOR]