Search Results (3)

Electrical contacts are of the greatest importance as they decisively contribute to the overall performance of photoresistors. Undoped κ-Ga₂O₃ is an ideal material for photoresistors with high performance in the UV-C spectral region thanks to its intrinsic solar blindness and extremely low dark current. The quality assessment of the contact/κ-Ga₂O₃ interface is therefore of paramount importance. The transfer length method is not applicable to undoped Ga₂O₃ because the interface with several metals shows a non-ohmic character, and a non-equivalent contact resistance could restrict its applicability. In this work, a new methodological procedure to evaluate the quality of contact interface and its effect on the sensing performance of UV-C photoresistors is presented, using the SnO_2−x/κ-Ga₂O₃ contact interface as a case study. The proposed method includes a critical comparison between two-point and four-point probe measurements, over a wide range of voltages. The investigation showed that the effect of contact resistance is more pronounced at low voltages. The presented method can be easily extended to any kind of metal/semiconductor or degenerate-semiconductor/semiconductor interface. Full article

A photodetector is a type of optoelectronic device with excellent photoelectric conversion abilities, which has especially important applications in many fields such as optical communication, image sensing, aerospace/environmental detection, and military safety. Among these applications, the multiplier effect of optoelectronic devices has been widely explored because photodetectors can convert a very weak optical signal into electrical signal output and offer amazing electron multiplication abilities. To date, hundreds of multiplier effects of photodetectors have been reported. However, there are few reviews on the multiplier effects of such devices. Here, a review of the multiplier effects of photodetectors covering detection spectra from ultraviolet to infrared is presented, including photodetectors based on inorganic materials, organic materials, and organic/inorganic materials. First, we provide brief insights into the detection mechanisms of multiplier effects of photodetectors and introduce the merits that represent key factors for a reasonable comparison of different photodetectors. Then, the multiplier effect on different types of material photodetectors is reviewed. Notably, we summarize the optimization directions of the performance of the multiplier photodetectors, including improving the external quantum efficiency, reducing the dark current, and increasing the response speed and spectral regulation. Finally, an outlook is delivered, the challenges and future directions are discussed, and general advice for designing and realizing novel high-performance photodetectors with multiplier effects is given to provide a guideline for the future development of this fast-developing field. The bottlenecks of existing multiplier technology are also analyzed, which has strong reference significance for the future development of this field. Full article

Black phosphorus (BP), owing to its distinguished properties, has become one of the most competitive candidates for photodetectors. However, there has been little attention paid on photo-response performance of multilayer BP nanoflakes with large layer thickness. In fact, multilayer BP nanoflakes with large layer thickness have greater potential from the fabrication viewpoint as well as due to the physical properties than single or few layer ones. In this report, the thickness-dependence of the intrinsic property of BP photodetectors in the dark was initially investigated. Then the photo-response performance (including responsivity, photo-gain, photo-switching time, noise equivalent power, and specific detectivity) of BP photodetectors with relative thicker thickness was explored under a near-infrared laser beam (λ_IR = 830 nm). Our experimental results reveal the impact of BP’s thickness on the current intensity of the channel and show degenerated p-type BP is beneficial for larger current intensity. More importantly, the photo-response of our thicker BP photodetectors exhibited a larger responsivity up to 2.42 A/W than the few-layer ones and a fast response photo-switching speed (response time is ~2.5 ms) comparable to thinner BP nanoflakes was obtained, indicating BP nanoflakes with larger layer thickness are also promising for application for ultra-fast and ultra-high near-infrared photodetectors. Full article