Study of Zinc Oxide Thin Films Deposited on Silicon Substrate by Atomic Layer Deposition
Date Issued
2007
Date
2007
Author(s)
Liao, Hung-Chang
DOI
zh-TW
Abstract
inc oxide is a II-VI semiconductor material with direct band-gap of 3.37eV corresponding to the light emission in the ultraviolet region. ZnO also has large excton binding energy (~60meV). In addition, ZnO can be used as transparent conducting oxide since it has low resistivity and high transparency in the visible region. As a result, ZnO is considered as a promising material for the application to the optoelectronics. In this thesis, we studied the growth of high-quality ZnO thin films on the silicon substrates by atomic layer deposition (ALD). We used two-step approach with high-temperature post-deposition annealing to grow ZnO with high (0002) orientation on the Si (111) substrate. It was shown that the crystal quality of the buffer layer significantly influenced the quality of the ZnO films. We also deposited the Al-doped ZnO (ZnO:Al) thin films to act as the transparent conducting oxide as well as the anti-reflection coating layer on the silicon substrates. The ZnO:Al thin film with the refractive index of 1.96 and the resistivity as low as 1.78×10-3 Ω-cm was achieved. The reflectivity of the ZnO:Al film on the silicon substrate was below 0.2% in the wavelength region between 545nm to 555nm. Finally, we deposited the n-type ZnO:Al thin film on the p-type silicon substrate with a thin Al2O3 surface-passivating layer to form an n-ZnO/Al2O3/p-Si tunneling diode. When the device was operated at reverse bias to act as a photodetector, the external quantum efficiency was up to 97.8% with the incident light at the wavelength of 532nm due to the anti-reflection coating effect of the ZnO:Al film. When the device was at forward bias, the holes in the p-type silicon tunneled into the defect states in ZnO:Al and then radiatively recombined with the electrons in ZnO:Al film, thus yielding an electroluminescence spectra at the wavelength at 590nm.
Subjects
原子層沉積技術
氧化鋅
透明導電層
抗反射層
光偵測器
發光二極體
atomic layer deposition
ZnO
transparent conducting oxide
anti-reflection coating
photodetector
light-emitting diode
Type
thesis
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