| 其他摘要 | As a member of group II-VI wide-band-gap semiconductors, MgxZn1-xO alloys are generating considerable interest as they can provide, in principle, an accessible band-gap range from around 3.37 eV (ZnO) to 7.8 eV (MgO). This makes them promising candidates for deep ultraviolet (DUV) optoelectronic devices. In the past decade, a large number of experiments have been conducted, focusing on solar-blind photodetection using MgZnO films, because of various important applications in missile tracking, flame detection, ozone layer monitoring, and so on. To date, however, most of the solar-blind photodetectors based on MgZnO have low-performance, especially in responsivity, which is one of the important figures of merit for DUV detectors to be commercially applied. Consequently, a controllable and high gain mechanism is required. This work foucs on the aforementioned problem, the main results were obtained as follows: 1. The gallium (Ga) doped cubic MgZnO films, which have been grown by metal organic chemical vapor deposition, have been obtained. It was demonstrated that Ga doping improves the n-type conduction of the cubic MgZnO films. A two-orders of magnitude enhancement in lateral n-type conduction have been achieved for the cubic MgZnO films. The responsivity of the cubic MgZnO-based photodetector has been also enhanced. Depletion region electric field intensity enhanced model was adopted to explain the improvement of quantum efficiency in Ga doped MgZnO-based detectors. 2. For MgxZn1-xO alloys, due to the wide tunable bandgap and a larger ratio of conduction-band offset to valence-band offset (ΔEC/ΔEV), it is very suitable for photon detection by using graded-band-gap technique. Via constructing heterojunctions based on p-Si/i-MgO/Graded-Band-Gap-Cubic-MgZnO, a solar-blind photodetector with enhanced and tunable gain have been demonstrated. The photodetector showed high performance, namely, high responsivity (1160 mA/W), quantum efficiency (600%), high sensitivity and selectivity towards the solar-blind spectrum, and fast response times (~ 15 µs). 3. A solar blind photodetector based on multilayers graded band gap cubic-MgZnO/i-MgO/p-Si has been demonstrated. The device exhibits a high responsivity wich is attributed to the photo-generated carriers impact ionization. This device structure will be more valuable in the field of low-noise solar-blind detection for its significant band alignment different between the conduction band and valence band. |
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