Solar-blind ultraviolet photodetector based on Nb2C/ß-Ga2O3heterojunction.

ß-Ga2O3has been widely investigated for its stability and thermochemical properties. However, the preparation ofß-Ga2O3thin films requires complex growth techniques and high growth temperatures, and this has hindered the application ofß-Ga2O3thin films. In this study,ß-Ga2O3thin films with good crystalline quality were prepared using a green method, and an ultraviolet (UV) detector based onß-Ga2O3with a photocurrent of 2.54 × 10-6A and a dark current of 1.19 × 10-8A has been developed. Two-dimensional materials have become premium materials for applications in optoelectronic devices due to their high conductivity. Here, we use the suitable energy band structure between Nb2C and Ga2O3to create a high carrier migration barrier, which reduces the dark current of the device by an order of magnitude. In addition, the device exhibits solar-blind detection, high responsiveness (28 A W-1) and good stability. Thus, the Nb2C/ß-Ga2O3heterojunction is expected to be one of the promising devices in the field of UV photoelectric detection.

A High-Performance UVA Photodetector Based on Polycrystalline Perovskite MAPbCl3/TiO2 Nanorods Heterojunctions.

The application of TiO2 nanorods in the field of ultraviolet (UV) photodetectors is hindered by a high dark current, which is attributed to crystal surface defects and intrinsic excitation by carrier thermal diffusion. Here, a photodetector based on polycrystalline perovskite MAPbCl3/TiO2 nanorods heterojunctions has been fabricated to overcome the shortcoming. The structure was composed of horizontal MAPbCl3 polycrystalline and vertically aligned TiO2 nanorods array. Many localized depletion regions at the MAPbCl3/TiO2 interface can reduce the dark current. The TiO2/MAPbCl3 detector shows high performance including a high ratio of light-dark current of about six orders of magnitude, which is much larger than that of the TiO2 detector. This study indicates the potential in the TiO2/MAPbCl3 heterojunction to fabricate high-performance UV detectors.

Timing Performance Simulation for 3D 4H-SiC Detector.

To meet the high radiation challenge for detectors in future high-energy physics, a novel 3D 4H-SiC detector was investigated. Three-dimensional 4H-SiC detectors could potentially operate in a harsh radiation and room-temperature environment because of its high thermal conductivity and high atomic displacement threshold energy. Its 3D structure, which decouples the thickness and the distance between electrodes, further improves the timing performance and the radiation hardness of the detector. We developed a simulation software-RASER (RAdiation SEmiconductoR)-to simulate the time resolution of planar and 3D 4H-SiC detectors with different parameters and structures, and the reliability of the software was verified by comparing the simulated and measured time-resolution results of the same detector. The rough time resolution of the 3D 4H-SiC detector was estimated, and the simulation parameters could be used as guideline to 3D 4H-SiC detector design and optimization.

A PFTBT modified visible-blind ultraviolet photodetector with a narrow detecting range and high responsivity.

A visible-blind ultraviolet (UV) photodetector (PD) based on TiO2/polyvinyl carbazole doped with poly {[2,7-(9-(20-ethylhexyl)-9-hexyl-fluorene])-alt-[5,50-(40,70-di-2-thienyl-20,10,30-benzothid-iazole)]} (PFTBT) was successfully fabricated. The introduced PFTBT exhibits high absorbance in the UV region and high conductivity which increases the device absorbance and the efficiency of carrier mobility. Besides, PFTBT acts as traps which can increase the concentration of the majority carrier. Therefore, the doped device exhibits high responsivity and high specific detectivity with the value of 0.22 A W-1 and 1.78 × 1012 Jones which respectively has a 3.6 and 2.6 times greater enhancement than the device without doping. The response time is also improved from 27 ms to 22 ms. Owing to the different absorbances that the materials have, the PD has a narrow detection range from 320 nm to 340 nm which is helpful to the study of the specific wavelength. In other words, the research provides a potential way to fabricate practical high-performance UVPDs.

The effect of self-depleting in UV photodetector based on simultaneously fabricated TiO2/NiO pn heterojunction and Ni/Au composite electrode.

A novel dark self-depleting ultraviolet (UV) photodetector based on a TiO2/NiO pn heterojunction was demonstrated and exhibited lower dark current (I dark) and noise. Both the NiO layer and Ni/Au composite electrode were fabricated by a smart, one-step oxidation method which was first employed in the fabrication of the UV photodetector. In dark, the depleted pn heterojunction structure effectively reduced the majority carrier density in TiO2/NiO films, demonstrating a high resistance state and contributing to a lower I dark of 0.033 nA, two orders of magnitude lower than that of the single-material devices. Under UV illumination, the interface self-depleting effect arising from the dissociation and accumulation of photogenerated carriers was eliminated, ensuring loss-free responsivity (R) and a remarkable specific detectivity (D*) of 1.56 × 1014 cm Hz1/2 W-1 for the optimal device. The device with the structure of ITO/TiO2/NiO/Au was measured to prove the mechanisms of interface self-depleting in dark and elimination of the depletion layer under UV illumination. Meanwhile, shortened decay time was achieved in the pn heterojunction UV photodetector. This suggests that the self-depleting devices possess the potential to further enhance photodetection performance.

Organics filled one-dimensional TiO2 nanowires array ultraviolet detector with enhanced photo-conductivity and dark-resistivity.

A heterojunction photo-conductive ultraviolet (UV) detector was developed based on TiO2 nanowires array (NWA) surrounded by N,N'-bis-(1-naphthalenyl)-N,N'-bis-phenyl-(1,1'-biphenyl)-4,4'-diamine (NPB). The novel and effective two-step method of static infusion and dynamic solution-cleaning was employed to fill NPB into TiO2 NWA gaps and simultaneously remove the unwelcomed top NPB layer. The device fabricated via the two-step method exhibited optimal performance compared to TiO2/NPB device with top NPB layer and TiO2 NWA device. In dark conditions, the TiO2/NPB heterojunction device without top NPB was found to possess the capacity of depleting majority carriers, thereby providing improved dark-resistivity to limit the dark current (Id). Under UV illumination, the depleting effect could be eliminated by the dissociation and accumulation of photo-generated carriers between pn heterojunction, leading to increased carrier density and photo-conductivity. It cleared up the high barrier due to the removal of top NPB layer, which was beneficial for hot electron transport than the device with top NPB layer under illumination, thereby achieving an enhanced light current (Il) to Id ratio of 1.67 × 104. A simple technology is provided to prepare organic-inorganic hybrid one-dimensional array heterostructure, which plays a remarkable role in the working of the UV detector, enhancing photo-conductivity and dark-resistivity of the device.