Growth Of Alxga1-Xn Thin Films On Silicon Using Sol-Gel Spin Coating Technique
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Date
2018-09
Authors
Nurul Atikah Mohd Isa
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Group-III nitrides such as aluminum nitride (AlN) and aluminum gallium nitride (AlGaN) have potential applications for ultraviolet light emitting devices and high power devices. Nowadays, sophisticated and expensive growth techniques are used to synthesize these thin films. Thus, an alternative method known as sol-gel spin coating method which is relatively cheap and simple as well as less explored was used to grow AlN and AlGaN thin films. In this work, the growth and characterization of AlN thin films on silicon (Si) substrate by sol-gel spin coating method under various nitridation parameters such as nitridation temperatures, nitridation durations, and ammonia (NH3) gas flow rates were investigated. For different nitridation temperatures, it was found that the full width at half maximum (FWHM) of AlN(002) diffraction peak of X-ray diffraction (XRD) and the E2(high) peak of Raman decreased, as the nitridation temperature increases from 1100 to 1150°C, which indicates the improvement of AlN crystal quality. The FWHM of both XRD and Raman increases when the nitridation temperature increased to 1200°C. This implied the degradation of AlN crystal. Moreover, the field-emission scanning electron microscopy (FESEM) image of sample nitridated at 1150°C showed a smooth and uniform surface with slightly bigger and densely packed grains as compared with that nitridated at 1100°C. As for nitridation durations, XRD showed the improvement of crystalline quality of AlN with increasing nitridation duration from 45 to 60 min.However, the crystalline quality of AlN degraded as the nitridation duration increases to 75 min due to nitrogen desorption might have occurred, thus restrict the formation of AlN. FESEM results showed that the grains are densely packed with a smooth and uniform surface was formed as the nitridation duration increases to 60 min. However, surface with unpacked and scattered grains was formed when the nitridation duration increases to 75 min. As for different NH3 flow rates, XRD and Raman results showed that the crystalline quality of AlN increases as the NH3 flow rate increases from 300 to 400 sccm. however, the AlN crystal quality degraded, as the NH3 flow rate increases to 500 sccm. The results revealed that the effective and optimum nitridation temperatures, nitridation durations, and NH3 flow rates for the growth of AlN thin films was 1150°C, 60 min, and 400 sccm, respectively. For the growth of AlxGa1-xN thin films on Si(111) substrate, AlN is used as buffer layer. The commercial AlN/Si(111) templates with 25 nm thickness is well-suited buffer layer for AlxGa1-xN thin films. AlxGa1-xN thin films with various Al composition were grown on the commercial AlN/Si(111) templates. XRD results showed that wurtzite AlGaN (GaN) thin films with preferred growth orientation of AlGaN(002) [GaN(002)] were successfully grown. However, the crystalline quality of the thin films degraded as Al composition increases. Overall, the results revealed that AlN and AlGaN thin films were successfully grown by sol-gel spin coating method. Eventually, these works may provide a new framework for the low-cost growth of AlN and AlGaN thin films by sol-gel spin coating method.
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Keywords
Thin films , Nanoelectronics