Fabrication of III-Nitride and Metal Chalcogen Heterostructure for Broadband Photodetection
Creators: name: Vashishtha, Pargam
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401805
subject: Nanofabrication, growth and self assembly
classificationCode: 401605
subject: Functional materials

description: Multispectral photodetection with autonomous light-detection capabilities, without any external voltage bias, holds substantial promise for revolutionizing energy-efficient technologies. Their significance extends to applications in the realms of the future memory devices to optically controlled logic gates. However, the commercial broadband detectors relying on traditional thin-film materials such as silicon, Mercury-cadmium-telluride and Indium-gallium-arsenide have relatively low tolerance against high operation temperature, which hinders their application in specialized domains from space surveillance to combustion monitoring. Therefore, an imperative necessity emerges for a self-bias photodetector endowed with an ultrabroad spectral detection capability, demonstrating robust performance even in elevated temperature conditions. Identifying an appropriate material for broadband photodetection under high-temperature circumstances has proven to be a persistent challenge.
Semiconductors with wider bandgaps become attractive candidates for the thermal stable photodetector; larger bandgaps reduce intrinsic-charge ionization effects due to thermal and radiation. The optical radiation detection range of these materials is confined to visible light. However, this limitation can be overcome by employing a heterostructure comprising a wide bandgap material in conjunction with the narrow bandgap material, thereby extending the detection range. The recent technological advancements have ushered in a significant breakthrough with the introduction of metal chalcogen semiconductors, offering a myriad of promising candidates that span nearly the entire spectrum of interest for photodetector exploration.
Laying a foundation, this study first addresses the quality of gallium-nitride (wide bandgap) thin film materials and explores their optoelectronic properties. On the other side of the coin, we aim for the growth of the different metal-chalcogens for the photodetection application. After these strategies, various heterostructures using metal-chalcogen thin film and gallium-nitride surface have been prepared for self-biased broadband photodetectors, yielding stability under elevated temperature conditions.
Chapter 1 introduces the background, motivations, literature survey and objectives of the research in this thesis. The research scopes of the thesis are defined. The identified research gaps are presented, and research questions are raised. The expected research outcomes/deliverables are demonstrated. 
Chapter 2 delineates the methodology of the ongoing research on gallium-nitride (GaN) and metal-chalcogens. The techniques employed for the growth of heterostructure and its bare counterpart material, along with detailed insights into characterizations and optoelectronic parameter assessments, are illustrated. 
Chapter 3 is based on the two published works on the growth optimizations of epitaxial GaN thin film for the optoelectronic application. Detailed self-bias photodetection properties of the GaN film under varying temperatures are presented. 
Chapter 4 is based on the four published works on the photodetection application of different metal-chalcogens thermal stability is also tested. On the other hand, make a heterostructure of the material that displays the thermally stable behaviour under high-temperature conditions. Besides, theoretical approaches are presented for the heterostructure to support our investigation. 
Chapter 5 revolves around four published works; each focus on diverse heterostructures created on the GaN surface by depositing various metal-chalcogen materials. The chapter highlights the performance of these heterostructures in terms of broadband photodetection and thermal stability under the self-bias mode of operation. Additionally, theoretical simulations have been conducted for the final heterostructure-based device to provide robust support for our research findings. 
Chapter 6 concludes the thesis and suggests the future direction of the research in the thesis.