Characterization of ZnO metal–semiconductor–metal ultraviolet photodiodes with palladium contact electrodes (original) (raw)
Related papers
Analysis on different detection mechanisms involved in ZnO-based photodetector and photodiodes
Journal of Materials Science: Materials in Electronics, 2020
The present study reports on the comparison between the ultraviolet (UV) light detection mechanisms in ZnO-based photodetectors and ZnO/PEDOT:PSS hybrid photodiodes. Using spray pyrolysis method, ZnO thin films were deposited upon glass substrates. The deposition temperature was varied from 350 to 425 °C and the physical properties of ZnO thin films were investigated. The structural analysis reveals that all the prepared ZnO thin films have a preferred orientation along the (002) plane with hexagonal wurtzite structure. The morphological analysis reveals that the grains are uniformly distributed. Electrical properties reveal that the ZnO thin film deposited at 425 °C shows a higher carrier concentration of 3.76 × 10 16 cm −3 with low electrical resistivity value of 2.59 × 10 2 Ω cm. For fabrication of UV photodetectors, the optimum ZnO layer with good electrical and optical property was deposited on ITO substrate with substrate temperature maintained at 425 °C. For the fabrication of hybrid UV photodiodes, poly (3,4 ethylene dioxythiophene):poly (styrene sulphonate) (PEDOT:PSS) and zinc oxide (ZnO) was used as the hole and electron transporting layers, respectively. The current-voltage (I-V) and photoresponse switching characteristics under UV light of the fabricated ZnO-based photodetector and photodiodes were studied and the detection mechanisms of such devices were analysed. It was observed that the ZnO-based photodiodes show higher photoresponsivity (R) value of 0.25 A/W with fast photoresponse switching speed.
Fabrication and Characterization of ZnO Photodetectors with High Gain
Journal of Nanoelectronics and Optoelectronics, 2010
We report fabrication and characterization of MSM UV photodetector based on Pd/ZnO thin film. The ZnO thin film was grown on glass substrate by thermal oxidation of pre-deposited zinc films by vacuum deposition technique. With applied voltage in the range from −3 V to 3 V we estimated the contrast ratio, responsivity, detectivity for an incident radiation of 0.1 mW at 365 nm wavelength. Our device exhibited a high gain which is attributed to the hole trapping at semiconductor-metal interface. I-V characteristics were studied by using microprobe arrangement. The parameter such as ideality factor, leakage current, resistance-area-product and barrier height were extracted from the measured data. The surface morphological and the structural properties of the thin film were studied by atomic force microscope.
Ultraviolet detectors based on ZnO:N thin films with different contact structures
Acta Physica Polonica Series a
Al/ZnO:N/Al and Ni/ZnO:N/Al diode photodetectors fabricated by dc magnetron sputtering of ZnO:N ¯lms on p-Si substrates are studied. The photocurrent-to-dark current ratio equal to 250 at ¸ = 390 nm and the time constant of photoresponse about 10 ¹s for Al/ZnO:N/Al structures with 4 ¹m interdigital spacing was achieved. The Ni/ZnO:N/Al diode structure has the recti¯cation ratio ¼ 102 at bias 1 V, the maximal responsivity about 0.1 A/W is observed at 365 nm, and the measured time constant of photore- sponse is about 100 ns.
Materials Science and Engineering: B, 2014
In this study, metal-semiconductor-metal (MSM) Schottky ultraviolet (UV) photodetectors were based on c-axis preferred oriented zinc oxide (ZnO) films, which were prepared on quartz substrates by radio frequency (RF) magnetron sputtering technique. The responsivity of the photodetector was enlarged greatly after annealing the MSM device. Meanwhile, the enhancement in the dark current that resulted from the experiment was accompanied by the increasing annealing temperature. The origin is preliminarily discussed combining the observations of dark currents and responsivities. The physical mechanism of the continuous annealing is proposed on the basis of metal-semiconductor contact theory and diffusion effect. By this model, Au atoms from the electrode play an important role in the Schottky barrier during annealing process. These results demonstrate that a simple route to improve the responsivities of photodetectors can be realized easily by annealing the devices.
Journal of Applied Physics, 2010
Ultraviolet photoconductivity relaxation in ZnO thin films deposited by rf magnetron sputtering are investigated. Effect of oxygen partial pressure in the reactive gas mixture and film thickness on the photoconductivity transients is studied. A different photodetector configuration comprising ZnO thin film with an ultrathin overlayer of metals like Cu, Al, Sn, Au, Cr, and Te was designed and tested. Photoresponse signal were found to be stronger ͑four to seven times͒ in these configurations than the pure ZnO thin films. Sn͑30 nm͒/ZnO sample exhibits highest responsivity of ϳ8.57 kV/ W whereas Te͑20 nm͒/ZnO structure presents highest sensitivity of ϳ31.3ϫ 10 3 compared to unloaded ZnO thin film. Enhancement in the photoresponse of ZnO thin films is attributed to the change in surface conductivity due to induced charge carriers at the interface because of the difference in work function and oxygen affinity values of metal overlayer with the underlying semiconducting layer. Charge carrier transfer from the metal layer to ZnO creates a surplus of electrons at the interface; a fraction of which are captured by the defect centers ͑traps͒ at the surface whereas the remaining one represents free carriers in the conduction band and are responsible for the enhanced photoconductivity.
Fabrication and characterization of ZnO film based UV photodetector
Journal of Materials Science: Materials in Electronics, 2008
ZnO films were deposited on Al 2 O 3 substrates by metalorganic chemical vapor deposition (MOCVD) at temperatures of 400, 450 and 500°C. The photoconductivity of the films has been analyzed for ultraviolet detector application. The changes in photoresponse and currentvoltage (I-V) are correlated with the deposition temperatures and microcrystalline structures. The study suggested that the photoresponse originating from bulk-and surfacerelated processes. For a film deposited at 400°C, a 1 ms fast rising time and a 5 ms fall time were observed. The photoresponsivity is *24 A/W with a 3 V bias.
Ga-doped ZnO (GZO) based ultraviolet photodetectors (PDs) were fabricated by dual ion beam sputtering with a metal–semiconductor–metal structure. The room-temperature operable PD demonstrated responsivity of 58 mA W À1 at zero bias, which is 15 times larger than that reported on similar material grown by a different physical vapour deposition process, with internal and external quantum efficiency values of $22.5% and 37.4%. The unbiased photodetection is attributed to the tunnelling of electrons due to heavy doping of GZO and built-in electric field due to different barriers at the two metal semiconductor contacts. The asymmetry in the electrodes was investigated by temperature-dependent current–voltage measurements.
Ultraviolet Photodetector based on Zin Oxide Thin Film Contacts
2020
This paper provides a general overview of the state of the art of ZnO thin film-based UV photodetector. It also discusses some recent UV photodetector based on ZnO thin film substrates developed in laboratory. The introduction section offers a background of the semiconductor thin filmbased devices and their applications. The few papers have been reviewed for the fabrication of ZnO thin film by using different technique and found significant results for the application in UV photodetector. Introduction Thin film technology is a very important tools in last few decades for providing high quality interconnection in many electronics and optoelectronics devices such as a flat-panel, photo detectors and solar cells. Thin film technology is very efficient method for using the performing device application that take advantage of high performance include sensors, flat panel display, micro electromechanical system, (MEMS), biomedical device and coating optical instruments, microwave and other...
Journal of Alloys and Compounds, 2020
Three different deposition techniques, hydrothermal, radio-frequency (RF) sputtering and vacuum coating techniques are utilized to prepare nanostructured ZnO thin films on p-type, boron doped, (100) Si substrates to fabricate planar Ag/ZnO/Al Schottky photodetectors. The surface topology and structural features of the nanostructured ZnO thin films were investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD). The electrical performance of the as fabricated Ag/ZnO Schottky diodes were investigated by according to their current-voltage (IeV) characteristics within a bias voltage range from À2 to þ2 V. The diode parameters such as saturation current, rectification ratio, and barrier height were estimated from the measured IeV characteristics. The study revealed that RF magnetron sputtering and vacuum thermal evaporation derived devices exhibit a lower turn on voltage and better rectification ratio compared with those of devices fabricated based on the hydrothermal method. On the other hand, the hydrothermal derived device offers a higher barrier height compared with that of other investigated devices. The UV detection properties of these photodetectors were investigated. Several important parameters, such as sensitivity, quantum efficiency and detectivity were explored. The study revealed that the sensitivity at À2 V for hydrothermal, RF sputtering, and vacuum evaporation devices, were 15.3, 6.5 and 2.8, respectively. The quantum efficiencies at-2 V for the hydrothermal, RF sputtering, and the vacuum derived Schottky photodetector were 98.8%, 84%, and 96.7%, respectively. The detectivities of hydrothermal, RF sputtering, and vacuum evaporation deposited devices at a voltage of À2 V were 7.66 Â 10 10 Jones, 5.03 Â 10 10 Jones, and 2.86 Â 10 10 Jones, respectively. These values suggest that the proposed nanostructured ZnO photodetectors can create new opportunities for lightweight, low cost and weak UV signal detection.
Sensors and Actuators A-physical, 2014
This paper reports the characterization of ZnO-based interdigitated metal-semiconductor-metal (MSM) Schottky barrier UV photodetectors fabricated by three methods. Specifically, devices having Pd Schottky contacts based on un-doped ZnO, Pd doped ZnO and Pd microplates embedded ZnO films. All ZnO films were grown on p-type Si 1 1 1 substrates by the sol-gel method. For embedded devices, Pd microplates where first grown on the substrate by thermal evaporation using a 80 m mesh shadow mask. We have estimated the photocurrent, contrast ratio, responsivity, and quantum efficiency of the photodetectors for applied voltage from −5 to 5 V and optical power from 50 to 200 W at 365 nm. The current-voltage characteristics were studied and parameters such as ideality factor, leakage current, and barrier height of the Schottky contacts were extracted. The barrier height dependence on the electric field and tunneling through the barrier has been taken into account of the studied MSM devices. The bandgap of both undoped ZnO and ZnO:Pd are evaluated from the absorbance spectra via double beam spectrophotometry. Surface morphology of the ZnO films was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). All devices showed a maximum photo-response at flat band voltages of MSMs. It was found that there is no significant difference between un-doped and Pd doped ZnO derived devices performance. The study also revealed that the Pd microplates embedded ZnO films resulted in devices exhibiting better photoresponse as compared to those using un-doped ZnO and ZnO:Pd thin films.