Biaxial strain effect on band structures and optical properties of GeSn/Ge quantum well

• Main Author: Ting, Shi En
• Other Authors: Fan Weijun
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/177132
• Institution: Nanyang Technological University

With the advancement and proliferation of technology, the use of Si photonics has become prevalent to realise the high performance of computers and energy efficient data transfer [1]. The use of Grp3-5 semiconductors has been a very promising prospect in various applications such as CMOS technology, laser structures and operations. With the increasing demand due to increasing amount of information being processed, the limits of conventional chips are reached in terms of power consumption and bandwidths [2]. This can be overcome by replacing the conventional chip design with optical devices like waveguides, modulators, detectors and lasers, in which information is processed via photons. Si, Ge and their alloys are indirect bandgap semiconductors, meaning that radiative processes in these materials are inefficient and slow [3]. Therefore, there is a need in finding suitable direct bandgap as it has higher absorption and higher emission compared to the indirect one. Particularly, GeSn semiconductor has been found to be very successful in the field of lasers. Growing Sn on Ge produces GeSn with the transition from an indirect to direct semiconductor. The GeSn layer is produced on bulk Ge substrate through epitaxial growth via CVD [4], forming a type-1 band alignment of the Ge/GeSn layers and as a result, a quantum well consisting of heterostructural Ge/GeSn/Ge layers, giving it incredible quality to firing speeds and high material gain in lasers. Due to the lattice mismatch of structures between Ge and Sn, biaxial compressive strain on GeSn layer is present [5].