Individual ZnO nanowires for photodetectors with wide response range from solar-blind ultraviolet to near-infrared modulated by bias voltage and illumination intensity

Abstract

ZnO nanowires have relatively high sensitivity as ultraviolet (UV) photodetectors, while the bandgap of 3.37 eV is an important limitation for their applications in solar-blind UV (SBUV), visible (VIS) and near infrared (NIR) range. Besides UV response, in this study, we demonstrate the promising applications of individual undoped ZnO NWs as high performance SBUV-VIS-NIR broad-spectral-response photodetectors, strongly depended on applied bias voltage and illumination intensity. The dominant mechanism is attributed to the existence of surface states in nanostructured ZnO. At a negative bias voltage electrons can be injected into surface states from electrode, and moreover, under light illumination photogenerated electron-hole pairs can be separated efficiently by surface built-in electric field, resulting into a decrease of potential barrier height and depletion region width, and simultaneously accompanying a filling of oxygen vacancy and a rise of ZnO Fermi level.

Glassy carbon/multi walled carbon nanotube/cadmium sulphide photoanode for light energy storage in vanadium photoelectrochemical cell

“…However, photocurrent changes are not spontaneous and show gradual variations. Similar behavior has been observed for other semiconductors such as ZnO nanowires [37], MoO 3 nonobelt [38] and Thylakoid-Carbon Nanotube Composites [39]. This behavior has been ascribed to the low sensitivity of photoelectrode to the light wavelength, light intensity and amount of applied bias potential.…”

Chemical bath deposited ZnO thin film based UV photoconductive detector

“…Correspondingly, the potential barrier height and depletion region width decreases. This in turn increases dark as well as UV photocurrent thereby decreasing the net photocurrent of the detector thus 5 V is supposed to be optimum bias voltage[33].These results indicate that present photodetector demonstrates a selectivity and sensitivity towards the UV-A light. The linear behavior of the I-V photocurrent curve confirms the good ohmic contact of photoconductive detector.…”

Effect of the buffer layer on the metal-semiconductor-metal UV photodetector based on Al-doped and undoped ZnO thin films with different device structures

“…At an applied bias voltage of 5 V a larger number of photogenerated electrons can cross the electrode/ZnO interface, whereas at lower applied bias voltage very few electrons could pass the interface, resulting in poor photoresponse. Furthermore, at a relatively higher bias voltage, the band‐edge response extends towards the visible region . This visible‐light response upon applying a relatively higher bias voltage is due the fact that, at higher bias voltage a higher number of electrons can be injected into the surface states of ZnO.…”

“…This visible‐light response upon applying a relatively higher bias voltage is due the fact that, at higher bias voltage a higher number of electrons can be injected into the surface states of ZnO. Thus, these electrons can also be filled into the depletion region, resulting into a reaction of V o + and V o ++ to V O , namely trap filling and correspondingly, the potential barrier height and depletion region width will decrease . The obtained photocurrent for the devices is much higher than the dark current.…”