Air-Stable, Solution-Processed Oxide p–n Heterojunction Ultraviolet Photodetector

Abstract

Air-stable solution processed all-inorganic p-n heterojunction ultraviolet photodetector is fabricated with a high gain (EQE, 25 300%). Solution-processed NiO and ZnO films are used as p-type and n-type ultraviolet sensitizing materials, respectively. The high gain in the detector is due to the interfacial trap-induced charge injection that occurs at the ITO/NiO interface by photogenerated holes trapped in the NiO film. The gain of the detector is controlled by the post-annealing temperature of the solution-processed NiO films, which are studied by X-ray photoelectron spectroscopy (XPS).

Self-powered p-NiO/n-ZnO heterojunction ultraviolet photodetectors fabricated on plastic substrates

“…The rise time ( t r ) for the photocurrent to reach from 10% to 90% of its maximum value, is ≈ 323 ms and the decay time ( t d ) for the photocurrent to decrease from 90% to 10% of the peak value, is ≈ 12 ms. The slow response of the PD is related to strong carrier trapping and these photoconductors exhibits comparable or better temporal response than other oxide based PDs 16, 18 indicating high quality engineered metal oxide heterojunction with excellent sensitivity. The devices also demonstrate an excellent UV-selective sensitivity with maximum UV-to-visible rejection ratio ( R λ=370 nm / R λ=450 nm ) of ≈ 183.…”

“…Among the variety of p-type materials that have been employed to form p-n junction with ZnO, p-NiO stands out due to its band alignment with ZnO and its alloys in UV PD applications. 15, 17, 18 Although excellent figures of merits have been achieved in NiO/ZnO PDs, most of the devices have been fabricated on rigid substrates using high processing temperature without any self-powered behavior 16, 17 which can limit their application on plastic substrates. On the other hand, some devices have shown very slow temporal response 18 that may not be suitable for high-speed device applications.…”

Transparent conductor-Si pillars heterojunction photodetector

“…[1][2][3][4][5][6] However, the biased operation 2,3,6 readily increases dark current values and, thus, easily decreases the photo-responses, besides the inevitable power dissipation.…”

“…ZnO-based UV photodetectors are usually photo-chemically reactive and showed slow responses. 2,[7][8][9] Nanostructures have attracted intensive interest due to their high aspect ratio; they provide an enlarged light-reactive surface that improves photo-responses 6,8,[10][11][12][13][14] Meanwhile, the difficulty of nanoscale fabrication is still holding back the progress of nanostructured photoelectric devices due to lack of uniform performance or reproducibility.…”

Growing Al2O3by Ultrasonic Spray Pyrolysis for Al2O3/AlGaN/GaN Metal-Insulator-Semiconductor Ultraviolet Photodetectors

“…Although PD-C had the highest EQE which was beyond 100%, but this degraded the gain bandwidth and operation speed of the PD-C. In addition to the internal gain, interfacial-trap controlled charge injection has been proposed to explain why the EQE excess 100% [23], [24]. The Al(OH) x and AlO x were found in the present Al 2 O 3 film in the XPS spectrum.…”