Ultraviolet optoelectronic devices based on AlGaN-SiC platform: Towards monolithic photonics integration system

Ultraviolet (UV) photodetectors based on wide-bandgap semiconductors are essential for next-generation sensing technologies operating in harsh and energy-limited environments. Because of its wide bandgap (3.26 eV), high thermal conductivity, and radiation tolerance, 4H-silicon carbide (4H-SiC) provides an ideal material foundation for realizing self-powered and deep-UV detection. However, the performance of these devices is often constrained by intrinsic defects, interface states, and recombination losses that limit charge transport and long-term stability, underscoring the urgent need for interface-driven design strategies. This review provides a comprehensive, mechanism-based overview of recent progress in self-powered 4H-SiC UV photodetectors, emphasizing interface engineering through heterostructure design, dielectric integration, and incorporation of carbon-based and 2D materials enables enhanced carrier separation, spectral selectivity, and device reliability. This work uniquely establishes quantitative correlations between interface properties and device figures of merit, highlights emerging architecture such as avalanche and phototransistor configurations, and discusses their scalability and integration prospects for autonomous UV sensing systems. By bridging material science, device physics, and system-level functionality, this review defines a unified framework for achieving high-efficiency, self-powered, and environmentally resilient 4H-SiC photodetectors, guiding future research toward scalable and intelligent UV detection technologies.

This review focuses on ultraviolet (UV) photodetectors based on wide bandgap semiconductors, which are gaining increasing attention for applications in defense, environmental monitoring, and biomedical fields. Materials such as ZnO and Ga₂O₃ offer high thermal stability, strong radiation resistance, and suitable band gaps for solar-blind UV detection. The paper summarizes various detector architectures' characteristics and device performance, including photoconductive, Schottky, metal–semiconductor–metal (MSM), p–n junction, and p–i–n junction types. Their responsivity, response time, dark current, and structural advantages are compared. Key performance enhancement strategies—doping, nanostructuring, and interface engineering—are discussed. Although significant progress has been achieved, challenges remain, including persistent photoconductivity, trade-offs between sensitivity and speed, and fabrication constraints. Future research should focus on novel materials, optimized device structures, and scalable integration techniques to enable high-performance and reliable wide bandgap UV photodetectors for next-generation optoelectronic systems.

Due to their large bandgap, high critical electric field, and availability of high-quality large-size melt-grown bulk substrates, III-oxides including Ga2O3, Al2O3, In2O3, and their alloys have been extensively investigated for a myriad of electronic and optoelectronic applications. Recently, β-Ga2O3 based power electronics, RF transistors, and ultraviolet (UV) photodetectors have been demonstrated with promising performance. However, p-type β-Ga2O3 is still elusive due to high dopant activation energy (>1 eV), large hole effective mass, and hole trapping. This significantly limits the design freedom for β-Ga2O3 devices. Other p-type semiconductors have been proposed to form heterostructures with β-Ga2O3 such as p-NiO, p-Cu2O, and p-type III-nitrides. As popular wide bandgap semiconductors, III-nitrides are promising candidates to form III-oxide/III-nitride heterostructures to enable advanced device structures and new functionalities. Furthermore, III-oxides and III-nitrides can be epitaxially grown on each other with small lattice mismatch (< 5% for GaN and β-Ga2O3) by the industrial standard epitaxial method MOCVD. For example, vertical GaN violet LEDs grown on n-type β-Ga2O3 substrates have been reported. This talk will present our recent work on III-oxide/III-nitride heterostructures in power electronics and optoelectronics.For power electronics, β-Ga2O3/GaN p-n heterojunctions will first be discussed. The heterojunction via mechanical exfoliation shows decent forward rectifying behaviors and thermal stability up to 200 °C but relatively low breakdown voltages (BV). To improve the breakdown capability, we carried out a comprehensive TCAD simulation study to design mesa edge termination for kV-class β-Ga2O3/GaN p-n heterojunctions. It was found that the electric field crowding effect is the main reason for the low BV. Several mesa edge termination structures were investigated such as deeply-etched mesa, step mesa, and p-GaN guard ring. Second, normally-off AlN/β-Ga2O3 field-effect transistors using polarization-induced doping will be discussed. A large two-dimensional electron gas is formed at the AlN/β-Ga2O3 interface due to polarization effects, and p-GaN gate is used to realize tunable positive threshold voltage. The device transfer and output characteristics with different device structures are also studied. For optoelectronics applications, self-powered spectrally distinctive Ga2O3/GaN heterojunction UV photodetectors grown by MOCVD will be discussed. Opposite current polarities are observed under different illumination wavelengths due to different carrier transports, which can be utilized to distinguish different spectra. These results indicate that (ultra)wide bandgap III-oxide/III-nitride heterostructures are a promising platform to enable new device structures and functionalities.

Enhanced UV photoresponse employing 3D graphene nanowalls/SnO2 nanocomposite film

Surface-acoustic-wave (SAW) based ultraviolet (UV) photodetectors with multiple optical sensing areas is presented by depositing patterned ZnO films on a LiNbO3 substrate. Two different types of electrodes, uniform interdigital transducer (IDT) and slanted finger interdigital transducer (SFIT), are designed and fabricated to analyze the performances of SAW array UV photodetectors. By tuning ultraviolet wavelengths, qualitative characteristics of SAW UV photodetectors are observed through the measurements of SAW attenuation. Quantitative analyses of the photodetectors are presented by varying light intensities. Moreover, dynamic responses of SAW array UV photodetectors under the illumination of different optical wavelengths are also demonstrated. Ultraviolet light of 350 nm with power densities of 8.46 and 18.34 μW/cm2 is detectable from a UV photodetector with uniform IDT and SFIT, respectively. This study not only indicates that a SAW-based UV sensor is a potential candidate of array UV photodetectors but also provides a comprehensive analysis of SAW UV photodetectors.

Synthesis of interface modified MoS2/ZnO heterostructure via simple hydrothermal method and their enhanced UV photodetection characteristics with ultrafast photoresponse speed

Due to their superior material properties, wide bandgap (WBG) semiconductors enable the application of power electronics at higher temperature operation, higher frequencies, and higher efficiencies compared to silicon (Si). However, the commonly-used aluminum wire bonding as topside interconnection technology prevents WBG semiconductors from reaching their full potential, due to inherent parasitic inductances, large size, heat dissipation, and reliability issues of wire bonding technology. Therefore, this article presents a comprehensive review of topside interconnection technologies of WBG semiconductor power devices and modules. First, the challenges and driving factors for the interconnection of WBG semiconductor dies are discussed. Second, for each widely commercially used WBG semiconductor, i.e., silicon carbide and gallium nitride, technical details and innovative features of state-of-the-art interconnection techniques in packages are reviewed. Then, the majority of existing topside interconnection materials for WBG semiconductors are categorized and compared, followed by a discussion of their advantages, challenges, and failure modes. Based on this elaborate discussion, potential future directions of the interconnection technology development are given. It is concluded that the superior performance of WBG semiconductors can be obtained by combining novel materials with innovative designs for the topside interconnections.

Wide band gap (WBG) semiconductors have progressively gained worldwide attention owing to their wide range of applications in commercially important devices, especially for energy- saving devices and energy harvesting technology. Energy harvesting is one of the vital emerging technologies of the modern era, referring to the collection of energy from the environment. In addition, WBG semiconductors are extensively used in high-performance electronic/optoelectronic devices due to their larger energy band gap, which allows them to absorb/emit a wide range of ultraviolet (UV) light. Recently, mixed wide band gap semiconductors have become more popular and attracted more attention of the researchers due to the possibility of tailoring the materials for specific device applications by adjusting the relative percentages of the constituent compounds, thereby enhancing device performance. A deep analysis of different types of WBG semiconductors and their various applications is crucial for the rapidly evolving modern world.

The ultraviolet (UV) photodetector has found many applications, ranging from optical communication to environmental monitoring. There has been much research interest in the development of metal oxide-based UV photodetectors. In this work, a nano-interlayer was introduced in a metal oxide-based heterojunction UV photodetector to enhance the rectification characteristics and therefore the device performance. The device, which consists of nickel oxide (NiO) and zinc oxide (ZnO) sandwiching an ultrathin dielectric layer of titanium dioxide (TiO2), was prepared by radio frequency magnetron sputtering (RFMS). After annealing, the NiO/TiO2/ZnO UV photodetector exhibited a rectification ratio of 104 under UV irradiation of 365 nm at zero bias. The device also demonstrated a high responsivity of 291 A/W and a detectivity of 6.9 × 1011 Jones at +2 V bias. Such a device structure provides a promising future for metal oxide-based heterojunction UV photodetectors in a wide range of applications.

Current state-of-the-art ultraviolet (UV) photodetectors are extensively used in applications ranging from industrial to biomedical science. As a result, there have been consistent efforts to improve their efficiency and to address challenges related to sensitivity and spectral selectivity. Two-dimensional (2D) materials, with their distinct properties, offer a promising solution due to their excellent UV detection characteristics. Additionally, their atomic scalability and CMOS compatibility enable easy integration with flexible platforms and current technologies. The exceptional optoelectronic characteristics, strong light-matter interaction, and quantum confinement in certain 2D materials have led to extensive investigations into 2D material-based UV photodetectors. This review provides a broad overview of the mechanisms of photodetection, various device configurations, and the current progress in both layered and non-layered 2D UV photodetectors. Finally, strategies for improving UV photodetection properties are discussed, along with a future outlook on the integration of 2D UV detectors into commercial platforms.

Au–MgO–ZnO (AMZ) ultraviolet (UV) photodetectors were fabricated to enhance their sensitivities by an inserting ultrathin insulating MgO layer. With the insulating layer, the sensitivities of the UV photodetectors were improved via the reduction of the dark current. Furthermore, strain modulation was used to enhance the sensitivities of the AMZ UV photodetectors. The sensitivities of the photodetectors were enhanced by the piezo-phototronic effect. However, there was a limiting value of the applied strains to enhance the sensitivity of the photodetector. When the external strains exceeded the limiting value, the sensitivity decreased because of the tunneling dark current. The external strains loaded on the photodetectors result in the degradation of the photodetectors, and an applied bias can accelerate the process. This work presents a prospective approach to engineer the performance of a UV photodetector. In addition, the study on the service behavior of the photodetectors may offer a strain range and theoretical support for safely using and studying metal–insulator–semiconductor (MIS) UV photodetectors.

Ga2O3/GaN hybrid ultraviolet (UV) photodetector (PD) has photon-carriers generated in the Ga2O3 region and transported in the GaN layer. In this work, by designing Ga2O3/GaN UV PD with a gate metal on the Ga2O3 surface, common-connected with the cathode on the GaN layer, we have revealed that the impact of substrate defects in the GaN region on the photo-generated carrier transport is significant for Ga2O3/GaN UV PD. As a result, we have observed asymmetric current in terms of the anode bias of different polarities. According to our measurement, the photocurrent of 8.81 × 10-5 A/cm2/2.34 × 10-5 A/cm2, the responsivity of 6.65 A/W/1.16 A/W, the rise time of 1.07 s/1.14 s, and the fall time of 1.16 s/1.35 s are achieved at the anode bias of -6 V/+6 V, respectively. When the anode is biased positively, the poorer performances are well attributed to the substrate defects, such that Ga2O3/GaN UV PD pushes the photo-generated carriers deep into the more defected GaN substrate region. This observation is further proven by the developed physical models.

20 - Metal oxide/carbon nanotube hybrid nanomaterials as ultraviolet photodetectors

Recent Advances in ZnO Based Ultraviolet Photodetectors

Ferroelectric materials have aroused increasing interest in the field of self‐powered ultraviolet (UV) photodetectors for their polarization electric field induced photovoltaic (PV) effect. However, the device performance of currently reported ferroelectric‐based self‐powered UV detectors remains to be improved. Herein, achievement of high‐performance ZnO/Pb0.95La0.05Zr0.54Ti0.46O3 (PLZT) heterojunction‐based self‐powered UV photodetectors is demonstrated by coupling the ferroelectric depolarization electric field (Edp) and built‐in electric field (EZnO/PLZT) at the ZnO/PLZT interface with a II‐type energy band alignment. The ZnO/PLZT heterojunction‐based self‐powered UV photodetector shows a remarkable responsivity (R = 3.96 mA W−1) and detectivity (D* = 6.6 × 1010 Jones), which are by two orders of magnitude larger than those of the device that are produced under similar conditions without ZnO layer. Moreover, the ZnO/PLZT heterojunction‐based device exhibits a rapid response (rise time τr = 0.04 s, decay time τd = 0.05 s), which is faster than most of previous reports. The excellent device performance of the ZnO/PLZT heterojunction‐based device can be attributed to the efficient separation and transport of photogenerated carriers caused by the constructive coupling of Edp and EZnO/PLZT. This work offers a feasible and effective strategy for the performance improvement of ferroelectric‐based self‐powered UV detectors.