The Effect Of Au Electrode Thickness On The Performance Of MgZnO UV Detector

ZnO has been recognized as one of the most promising candidates for solar-orvisible-blind UV photodetectors due to their special properties, such as low defect density,high radiation hardness, environment friendly, and continuous tunable band gap (3.3eV-7.8eV) by the incorporation of Mg. Till now, many kinds of MgZnO UV detectors have beenfabricated trough different methods, and most studies have been concentrated on how toimprove the performance of the detectors. As is well known, the metal electrode is animportant part of semiconductor ultraviolet detectors, through which the bias voltage can beapplied to the device and the electric signals can be collected. However, the metal electrode,which has a strong absorption of ultraviolet light, will reduce the external quantum efficiencyof the device. Thus, the material, the structure and the thickness of electrode would havesignificant effects on the devices’ performance. For a given electrode geometry and material,the transmittance and the conductivity of the electrode are strongly dependent on the electrodethickness, i.e. thinner electrode has higher transmittance and lower electrical conductivity,while thicker one is just the opposite. Therefore, choosing the appropriate thickness of themetal electrode is an effective method to improve the performance of UV detectors. Based on the research status of MgZnO films and detectors, MgZnO UV photodetectors with differentAu electrode thicknesses have been demonstrated and investigated in this thesis to find out theoptimal electrode thickness. The main research works are as follows:1. We fabricated MgZnO films with different Mg fractions by tuning the temperature ofMg and Zn sources using the molecular beam epitaxy (MBE) equipment, and the structuraland optical properties of MgZnO films have been investigated. This would provide thematerial foundation for the realization of MgZnO UV detector.2. Au electrodes were prepared on the MgZnO thin films using the ion sputtering equipmentto realize the Au-MgZnO-Au structure UV photodetectors. By adjusting the sputtering time,the devices with different Au electrode thicknesses can be demonstrated. We measured theresponse spectra, the dark current, and so on. With increasing the Au electrode thicknessfrom0to32nm, the responsivity of the MgZnO UV photodetectors increases firstly andthen decreases. And when the Au electrode thickness is28nm, the responsivity reaches themaximum value.