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Surface modification of AlN using organic molecular layer for improved deep UV photodetector performance
摘要： Direct wide bandgap of 6.2 eV, high temperature robustness and radiation hardness make aluminum nitride (AlN) a preferable semiconductor for deep ultraviolet (UV) photodetection. However, the performance and reliability of AlN- based devices is adversely affected by a large density of surface states present in AlN. In this work, we have investigated the potential of a monolayer of organic molecules in passivating the surface states of AlN which improved the performance of AlN- based metal- semiconductor- metal (MSM) deep UV photodetectors. The organic molecules of Meso-5,10,15-triphenyl-20-(p-hydroxyphenyl)porphyrin Zn(II) complex (ZnTPP(OH)) were successfully adsorbed on AlN surface, forming a self- assembled monolayer (SAM). The molecular layer was characterized by contact angle measurement, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The surface modification of AlN effectively reduced dark current of the photodetector by ten times without degrading the magnitude of photo current, especially at low voltages. Photo to dark current ratio (PDCR) was enhanced from 930 to 7835 at -2V and the responsivity doubled from 0.3 mA/W to 0.6 mA/W at 5V. Moreover, the rise and fall times of the detector were found to decrease after the surface modification process. Our results suggest that SAM of porphyrin molecules effectively passivated the surface states in AlN which resulted in improved photodetector performance.
关键词： Dark current,PDCR,MSM UV photodetector,Surface states,SAM,Responsivity,Temporal response
更新于2025-09-23 15:19:57
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Dip coated TiO2 based metal-semiconductor-metal ultraviolet photodetector for UV A monitoring
摘要： Metal-Semiconductor-Metal ultraviolet photodetector was fabricated by painting silver contacts on dip coated TiO2 thin films. The number of deposition cycles have influence on physiochemical properties and UV sensing properties. The UV photodetector properties were studied by illuminating devices with light intensity of 1.8 μW/cm2 and 5 V bias. The fabricated devices show ohmic I–V characteristics. The maximum photocurrent of 0.64 μA is obtained at 365 nm for film deposited at 8 cycles. The highest photoresponsivity obtained for C8 sample under UV illumination of 365 nm is 2.15 A/W at 5 V bias. The fast rise and fall times obtained for fabricated device are 17 s and 19 s. The optical switching characteristics show good reproducibility and stability.
关键词： Photoresponsivity,Dip coating,MSM UV photodetector,Titanium dioxide
更新于2025-09-23 15:19:57
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Hydrothermally-Grown TiO2 Thin Film-Based Metal–Semiconductor–Metal UV Photodetector
摘要： A metal–semiconductor–metal (MSM) ultraviolet photodetector has been fabricated by using hydrothermally-grown TiO2 thin films. Ag paint was used as a contact electrode which showed the good ohmic contact between the metal–semiconductor junctions. The effect of deposition time on the structural, morphological and photodetector properties have been studied. The prepared TiO2 thin films are polycrystalline and show a rutile crystal structure with the preferred orientation along the (110) plane. The MSM UV photodetector was illuminated under a UV lamp with an intensity of 1.8 lW/cm2 and at 5-V bias. The photocurrent of the device increased linearly with the applied voltage. The maximum photocurrent of 3.96 lA was obtained for the film deposited at 5 h and maximum spectral photoresponsivity was 13.29 A/W. The device showed a fast optical switching behavior. The high responsivity and fast photoresponse shows that fabricated TiO2 detectors are good candidates for ultraviolet photodetectors.
关键词： MSM UV photodetector,Titanium dioxide,photoresponsivity,hydrothermal method
更新于2025-09-19 17:13:59