Optical Characterisation of Dry Etched II-VI Semiconductors

Smart, Andrew Patrick (1994) Optical Characterisation of Dry Etched II-VI Semiconductors. PhD thesis, University of Glasgow.

Abstract

The topic of this thesis is the characterisation of dry etched II-VI semiconductors. After a brief introduction to the thesis there follows a review of the literature on the subjects encompassed by the thesis. The subjects covered include the development of the growth process and fabrication techniques. Also included is a summary of the theoretical aspects which have driven experimental research into nanotechnology. There is a fairly rigorous description of the experimental apparatus used during the project which is split into spectroscopy equipment and fabrication equipment for reasons of clarity. The samples used in the course of the project are also described. This is followed by an intensive explanation of the theory behind the experimental techniques used in the assessment of the materials, specifically Raman scattering and photoluminescence spectroscopy. There is also a brief account of some crystallographic information concerning tellurium which is of relevance to this work. The results are presented for each material considered, namely zinc selenide and zinc telluride. For each material the results are presented first for photoluminescence and then for Raman scattering. Each of these techniques was used to examine the samples as-grown and after a uniform etch was performed on the unpatterned samples using the technique of dry etching. The etch gas chemistry used was methane and hydrogen, the use of which to etch II-VI semiconductors was pioneered at Glasgow University. The experimental procedure is reported which was developed to fabricate wires and dots with dimensions down to 20 nm in zinc telluride. Use was made of electron-beam lithography to pattern a bilayer of positive electron-beam resist spun on the sample. The nanostructures were then characterised using the above optical spectroscopic techniques. The effect on the Raman scattering process of varying numerous parameters was investigated, these being excitation frequency and power, sample temperature and excitation polarisation. The difference between the region patterned with nanostructures and the region away from the pattern was explored, as was the orientation of the wires with respect to the incoming laser radiation in the near back scattering configuration used. The results of the experiments are discussed, paying particular consideration to the theoretical aspects discussed earlier concerning the confinement of phonons and crystalline damage. The subject of hydrogen incorporation and subsequent passivation of luminescence centres is broached. Relevant conclusions are then drawn from the results and discussion. Suggestions for extending the work covered in this thesis and any other work considered to be of interest concerning this project are then put forward.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Clivia Sotomayor Torres
• Keywords: Electrical engineering, Optics
• Date of Award: 1994
• Depositing User: Enlighten Team
• Unique ID: glathesis:1994-75737
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Dec 2019 09:15
• Last Modified: 19 Dec 2019 09:15
• URI: https://theses.gla.ac.uk/id/eprint/75737