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Dr Matthew Sharpe

My publications


Sharpe M. K., Marko I. P., Duffy D. A., England J., Schneider E., Kesaria M., Fedorov V., Clarke E., Tan C. H., Sweeney S. J. (2019) A comparative study of epitaxial InGaAsBi/InP structures using Rutherford backscattering spectrometry, X-ray diffraction and photoluminescence techniques,JOURNAL OF APPLIED PHYSICS 126 (12) 125706 AMER INST PHYSICS
In this work, we used a combination of photoluminescence (PL), high resolution X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) techniques to investigate material quality and structural properties of MBE-grown InGaAsBi samples (with and without an InGaAs cap layer) with targeted bismuth composition in the 3%?4% range. XRD data showed that the InGaAsBi layers are more homogeneous in the uncapped samples. For the capped samples, the growth of the InGaAs capped layer at higher temperature affects the quality of the InGaAsBi layer and bismuth distribution in the growth direction. Low-temperature PL exhibited multiple emission peaks; the peak energies, widths, and relative intensities were used for comparative analysis of the data in line with the XRD and RBS results. RBS data at a random orientation together with channeled measurements allowed both an estimation of the bismuth composition and analysis of the structural properties. The RBS channeling showed evidence of higher strain due to possible antisite defects in the capped samples grown at a higher temperature. It is also suggested that the growth of the capped layer at high temperature causes deterioration of the bismuth-layer quality. The RBS analysis demonstrated evidence of a reduction of homogeneity of uncapped InGaAsBi layers with increasing bismuth concentration. The uncapped higher bismuth concentration sample showed less defined channeling dips suggesting poorer crystal quality and clustering of bismuth on the sample surface.
This thesis investigates novel range semiconductor materials and structures for use in optoelectronic devices operating from UV to mid-IR. These devices have an abundant variety of applications, including optical communications and imaging. The studies primarily focus on the electronic band structure of the materials and how this impacts device performance. Dilute bismide III-V alloys are a material of great interest for IR applications, especially with the band structure engineering that can be carried out to fulfil the condition where the spin-orbit splitting energy, ?