The Study of MgxZn1-xO Dual-Band Metal-Semiconductor-Metal Photodetector with Different Thicknesses by RF Magnetron Sputter

• Main Authors: LIAO, WEI-HSU, 廖偉旭
• Other Authors: WANG, CHUN-KAI
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/bkj4vb

碩士 === 南臺科技大學 === 電子工程系 === 107 === It is well known that zinc oxide (ZnO) is a non-toxic, inexpensive, and thermally stable wide band-gap material. It is widely used in thin-film transistor and ultraviolet photodetector. The energy bandgap of magnesium zinc oxide (MgZnO) can be changed with the modulation of magnesium content, which can detect a light wavelength up to 200 nm and can be used in UVA, UVB, and UVC photodetector. In this study, the different thicknesses of thin film ZnO/MgZnO were deposited on quartz substrate by the RF magnetron sputtering technique and its thin film properties were physically analyzed by SEM, XRD, XPS, PL and spectroscope. Then, a dual-band metal-semiconductor-metal (MSM) photodetector was fabricated by inserted an isolating layer of silicon dioxide (SiO2) between the ZnO and MgZnO and its optoelectronic properties were also investigated. There were three parts of the proposed experiment. First, a dual-band photodetector was fabricated by the stacking of the thin films of MgZnO with 10% and 20% magnesium content. The response characteristic of this dual-band photodetector was poor due to the diffusion of the magnesium atoms. Thus, we attempted to insert a layer of SiO2 to avoid the diffusion of the magnesium atoms. In order to further improve the dual-band characteristic of photodetector, in the third part of the experiment, the bottom layer of MgZnO with 10% magnesium content was replaced by ZnO. And, upper layer of MgZnO with 20% magnesium content was deposited with the thicknesses of 100 nm, 150 nm, and 200 nm, respectively, on top of the SiO2 isolating layer. It was found that the ZnO/MgZnO photodetector with a MgZnO thickness of 200 nm showed a lower dark current and better dual-band response. Such a result is attributed to the larger grain size and higher absorptive response of MgZnO as the thickness of MgZnO increased. Therefore, we successfully fabricate a significantly better response of the dual-band ZnO/MgZnO photodetector.