Indian Institute of Science
Yaddanapudi, G R Krishna.
Effect of Process Parameters on the Growth of N-Polar GaN on Sapphire by MOCVD.
Degree: PhD, Faculty of Engineering, 2017, Indian Institute of Science
Group III-Nitrides (GaN, InN & AlN) are considered one of the most important class of semiconducting materials after Si and GaAs. The excellent optical and electrical properties of these nitrides result in numerous applications in lighting, lasers, and high-power/high-frequency devices. Due to the lack of cheap bulk III- Nitride substrates, GaN based devices have been developed on foreign substrates like Si, sapphire and SiC. These technologies have been predominantly developed on the so called Ga-polarity epitaxial stacks with growth in the  direction of GaN. It is this orientation that grows most easily on sapphire by metal organic chemical vapor deposition (MOCVD), the most common combination of substrate and deposition method used thus far. The opposite [000¯1] or N-polar orientation, very different in properties due to the lack of an inversion centre, offers several ad- vantages that could be exploited for better electronic and optoelectronic devices. However, its growth is more challenging and needs better understanding.
The aim of the work reported in this dissertation was a systematic investigation of the relation between the various growth parameters which control polarity, surface roughness and mosaicity of GaN on non-miscut sapphire (0001) wafers for power electronics and lighting applications, with emphasis on the realization of N-polar epitaxial layers. GaN is grown on sapphire (0001) in a two-step process, which involves the deposition of a thin low temperature GaN nucleation layer (NL) on surface modified sapphire followed by the growth of high temperature device quality GaN epitaxial layer. The processing technique used is MOCVD. Various processing methods for synthesis of GaN layers are described with particular em- phasis on MOCVD method. The effect of ex situ cleaning followed by an in situ cleaning on the surface morphology of sapphire (0001) wafers is discussed. The characterization tools used in this dissertation for studying the chemical bond nature of nitrided sapphire surface and microstructural evolution (morphological and structural) of GaN layers are described in detail.
The effect of nitridation temperature (TN) on structural transformation of non- miscut sapphire (0001) surface has been explored. The structural evolution of nitrided layers at different stages of their process like as grown stage and thermal annealing stage is investigated systematically. The chemical bond environment information of the nitrided layers have been examined by x-ray photoelectron spectroscopy (XPS). It is found that high temperature nitridation (TN ≥ 800 °C) results in an Al-N tetrahedral bond environment on sapphire surface. In contrast, low temperature nitridation (TN = 530 °C) results in a complex Al-O-N environment on sapphire surfaces. Microstructural evolution of low temperature GaN NLs has been studied at every stage of processing by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Surface roughness evolution and island size distribution of NLs measured from AFM…
Advisors/Committee Members: Banerjee, Dipankar (advisor), Raghavan, Srinivasan (advisor).
Subjects/Keywords: Semiconductors; Nitrides; Gallium Nitride; N-Polar Gallium Nitride; Metal Organic Chemical Vapor Deposition (MOCVD); Galllium Nitride Growth; High Temperature Gallium Nitride; Low Temperature Gallium Nitride; GaN; Materials Engineering
to Zotero / EndNote / Reference
APA (6th Edition):
Yaddanapudi, G. R. K. (2017). Effect of Process Parameters on the Growth of N-Polar GaN on Sapphire by MOCVD. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2662
Chicago Manual of Style (16th Edition):
Yaddanapudi, G R Krishna. “Effect of Process Parameters on the Growth of N-Polar GaN on Sapphire by MOCVD.” 2017. Doctoral Dissertation, Indian Institute of Science. Accessed January 23, 2021.
MLA Handbook (7th Edition):
Yaddanapudi, G R Krishna. “Effect of Process Parameters on the Growth of N-Polar GaN on Sapphire by MOCVD.” 2017. Web. 23 Jan 2021.
Yaddanapudi GRK. Effect of Process Parameters on the Growth of N-Polar GaN on Sapphire by MOCVD. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2017. [cited 2021 Jan 23].
Available from: http://etd.iisc.ac.in/handle/2005/2662.
Council of Science Editors:
Yaddanapudi GRK. Effect of Process Parameters on the Growth of N-Polar GaN on Sapphire by MOCVD. [Doctoral Dissertation]. Indian Institute of Science; 2017. Available from: http://etd.iisc.ac.in/handle/2005/2662