The Fabrication And Characterization Of Mixed-phase MgZnO Thin Films And Their Ultraviolet Detectors

Effect of interface types, the ratio of hexagonal structure MgZnO on the solar-blind UV responsivity and signal to noise ratio of mix-structure MgZnO thin films were studied, and the performance of Au/MgZnO/Ga doped ZnO /In detector based on vertical cubic MgZnO/ hexagonal Ga doped Zn O mix-structure systerm was also studied. The main research contents are listed as follows:1. Mix-phase MgZnO thin films with(200) cubic MgZnO/(0002) hexagonal MgZn O interfaces and mix-phase MgZnO thin films with(111) cubic MgZnO/(0002) hexagonal MgZnO interfaces were deposited under certain conditions by PLD method. Because of the high internal gain from high density of interface states density between(200) cubic structure MgZnO grains and(0002) hexagonal structure MgZnO grains, the peak responsivity of the detector based on mixed-structure MgZnO thin film with(200) cubic MgZnO/(0002) hexagonal MgZnO interfaces reached 8A/W at 256 nm under 25 V bias voltage, which was two orders of magnitude higher than the sample with(111) cubic MgZn O/(0002) hexagonal MgZnO interfaces, and the internal gain of the detector reached 3809%. Because the barrier height was higher at(111) cubic MgZnO/(0002) hexagonal MgZnO interfaces, the Idark of the detector with(111) cubic MgZnO/(0002) hexagonal MgZnO interfaces was only 0.5nA under 5V bias voltage, which was three orders of magnitude smaller than the detector with(200) cubic MgZnO/(0002) hexagonal MgZnO interfaces, and the Ilight/Idark ratio and signal/noise ratio of which was also higher.2. MgZnO thin films with different hexagonal MgZnO compositions were prepared under different laser energy on quartz substrate and sapphire substrate. The content of Zn in MgZnO thin films and the composition of hexagonal MgZnO increased with the laser energy, and the UV absorb edge of MgZnO thin films shifted toward higher wavelength. The UV responsivity of the MgZnO photodetectors increased and the peak responsivity positions shifted toward higher wavelength when the content of hexagonal MgZnO increased in MgZnO thin films on both substrates.3. The Au/MgZnO/ZnO:Ga/In vertical structure UV detector was made. Because the hotogenerated carriers generated in Ga-doped ZnO thin film were blocked by the higher barrier height between cubic MgZnO and Ga-doped ZnO interfaces, thus the Au/MgZnO/ZnO:Ga/In vertical structure UV detector showed maximum response at 242 nm, which agree with the UV response characteristics of cubic MgZnO thin film in the detector.