Growth And Characterizations Of Spin Coated Gallium Nitride Thin Films On Siliconsubstrates
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Date
2016-03
Authors
Fong, Chee Yong
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Publisher
Universiti Sains Malaysia
Abstract
Gallium nitride (GaN) which has a direct band gap of 3.4 eV has become the focus of materials research. This is due to its unique combination of properties and technological importance for use in various applications such as optoelectronic devices and high power electronic devices. Various conventional methods have been developed to synthesize GaN thin films in the past few decades. However, there are only a few reported studies dealing with the growth of GaN thin films by using sol-gel spin coating method which is simpler and cheaper as compared to the conventional methods. Thus, the main objective of this work is to grow GaN thin films using sol-gel spin coating method. The initial phase of this work involved the synthesis and characterization of GaN thin films grown by using sol-gel spin coating method without diethanolamine (DEA). The results show that the growth of GaN thin films was not successful by using this method. With the aid of DEA, the results reveal that highly c-oriented wurtzite GaN thin films were successfully grown. This is mainly due to the DEA with higher viscosity was able to increase the viscosity of the precursor. Through these studies, it was found that optimum nitridation temperatures and durations are 950 °C and 75 min, respectively. While the successful growth of c-oriented GaN thin films requires a formation of metastable amorphous gallium (I) oxide (Ga2O). Due to various issues of the RF sputtering system, the quality of the home grown aluminium nitride (AlN) buffer layers was inconsistent. Consequently, this has hindered the growth of GaN thin films. To overcome this issue, commercial AlN templates were used. The effects of AlN buffer layer thickness on the growth of the GaN thin films were investigated. All the results revealed that AlN buffer layer with thickness of 25 nm was the suitable thickness for the growth of good quality GaN thin films. The effects of the number of coated process cycle on the crystalline quality of deposited GaN thin films were also investigated. Finally, GaN-based UV photodetector was fabricated. Platinum Schottky contacts were deposited by using a metal-semiconductor-metal pattern mask. Current-voltage measurements were performed in the dark and ultraviolet illuminated conditions. The photocurrent was found to be increased with the illumination of UV light. The Schottky barrier height (SBH) evaluated at room temperature (298 K) was found to be 0.35 eV and 0.34 eV for dark current and photocurrent, respectively. The obtained SBH values are in reasonable agreement with the reported values. Overall, the results revealed that wurtzite structure GaN thin film with GaN(002) preferential orientation was successfully deposited on AlN/Si(100) substrates by sol-gel spin coating method with the aid of DEA and the synthesis is reproducible.
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Keywords
Gallium nitride (GaN)