American Journal of Nano Research and Applications
Volume 7, Issue 1, March 2019, Pages: 6-10
Received: Jul. 19, 2019;
Accepted: Jul. 31, 2019;
Published: Sep. 2, 2019
Views 378 Downloads 66
Ahmed Mohammed Nahhas, Department of Electrical Engineering, Faculty of Engineering and Islamic Architecture, Umm Al Qura University, Makkah, Saudi Arabia
In this paper, ultraviolet (UV) detection properties of epitaxial ZnO films grown on sapphire substrates with radio-frequency magnetron sputtering is reported. The responsivity (R) of the ZnO photoconductors measured at 325 nm wavelength shows a strong dependence on the incident power (P), i.e., R µ P-k (k = 0.7). A responsivity of 3500 A/W (or a gain of 6000) is obtained at the optical power density of 10-7 W/cm2, and the value decreases to 1 A/W at 10-2 W/cm2. The ultra-high responsivity at the low power regime suggests a long lifetime (order of 10 ms) of carriers. The enhanced carrier lifetime is explained by the preferential capture of holes at the recombination centers that exist in the depletion region around grain boundaries and film surface, and the subsequent separation of photogenerated carriers. The strong dependence of the responsivity on the incident power is attributed to the modulation of space charge region width by the photogenerated holes and the resulting change in carrier lifetime.
Ahmed Mohammed Nahhas,
High Responsivity Ultraviolet Photoconductors Based on Epitaxial ZnO Thin Films, American Journal of Nano Research and Applications. Special Issue: Recent Advances of Nanomaterials and Devices.
Vol. 7, No. 1,
2019, pp. 6-10.
P Meng, S Gu, J Wang, J Hu, J He, “Improving electrical properties of multiple dopant ZnO varistor by doping with indium and gallium,” Ceramics International 44, 1168-1171, (2018).
C Fei, H Hsu, A Vafanejad, Y Li, Q Zhou, “Ultrahigh frequency ZnO silicon lens ultrasonic transducer for cell-size microparticle manipulation,” Journal of Alloys and Compounds, 729, 556-562, (2017).
B Sarma, BK. Sarma, “Role of residual stress and texture of ZnO nanocrystals on electro-optical properties of ZnO/Ag/ZnO multilayer transparent conductors,” Journal of Alloys and Compounds 734, 210-219, (2018).
M Zhang, H Zhang, L Li, K Tuokedaerhan, Z Jia, “Er-enhanced humidity sensing performance in black ZnO-based sensor,” Journal of Alloys and Compounds 744, 364-369, (2018).
Q Sun, Y Men, J Wang, S Chai, Q Song, “Support effect of Ag/ZnO catalysts for partial oxidation of methanol,” Inorganic Chemistry Communications 92, 51-54, (2018).
J Kim, B Kang, H Jeong, S Kim, S Kang, “Quantum dot light emitting diodes using size-controlled ZnO NPs,” Current Applied Physics 18, 681-685, (2018).
S Safa, S Mokhtari, A Khayatian, R Azimirad, “Improving ultraviolet photodetection of ZnO nanorods by Cr doped ZnO encapsulation process,” Optics Communications 413, 131-135, (2018).
D You, C Xu, F Qin, Z Zhu, W Liu. “Interface control for pure ultraviolet electroluminescence from nano ZnO based heterojunction devices,” Science Bulletin 63, 38-45, (2018).
S Park, W Hong, J Kim, “Piezoelectric and spontaneous polarization effects on exciton binding energy and light emission properties of wurtzite ZnO/MgO quantum dots,” Solid State Communications 261, 21-25, (2017).
X Liang, L Shen, “Interfacial thermal and electrical transport properties of pristine and nanometer-scale ZnS modified grain boundary in ZnO polycrystals,” Acta Materialia 148, 100-109, (2018).
K Liu, M Sakurai, M Aono, “ZnO based ultraviolet photodetectors,” Sensors 10, 8604-8634 (2010).
L Vikas, K Vanaja, P Subha, M Jayaraj, “Fast UV sensing properties of n-ZnO nanorods/p-GaN heterojunction,” Sensors and Actuators A: Physical 242, 116-122, (2016).
C Pemmaraju, TArcher, R Hanafin, S Sanvito, “Investigation of n-type donor defects in Co-doped ZnO,” Journal of Magnetism and Magnetic Materials 316, 85-187, (2007).
Ahmed Nahhas, H Kim, J Blachere, “Epitaxial growth of ZnO films on Si substrates using an epitaxial GaN buffer,” Applied Physics Letters 78, 1511, (2001).
Ahmed Nahhas, “Study of ZnO Epitaxial growth and MSM photodetectors,” University of Pittsburgh (2001).