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Title: Growth and characterization of bulk GaAs1-xBix/GaAs diodes
Author: Hunter, Christopher
ISNI:       0000 0001 2424 6695
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2014
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To explore the feasibility of utilising gallium arsenide bismide (GaAsBi) as a material for use in solar cells, undoped GaAsBi layers ranging from 50 nm to 350 nm in thickness have been grown by molecular beam epitaxy (MBE) in a p-i-n diode configuration. A growth interrupt technique was employed in order to avoid accumulation of excess surface bismuth. X-ray diffraction measurements showed that GaAs1-xBix with x~0.06 can be grown up to at least 100 nm thick with negligible strain relaxation. The GaAsBi layers are highly uniform and free from the common phenomenon of phase separation; however transmission electron diffraction measurements show the presence of CuPt-type ordering. The structures were processed into devices using a combination of photolithography and wet etching. The electrical characteristics of the devices were investigated using current-voltage and capacitance-voltage measurements. The absorption properties of the devices were systematically investigated by measuring the photocurrent both at a fixed wavelength of 1064 nm and over a range of wavelengths. The samples containing GaAsBi layers showed a photoresponse in the near-infrared up to almost 1.3 μm. The absorption coefficients of the layers were obtained from the responsivity data. Below the band gap, the absorption coefficients showed an exponential dependence on the photon energy (Urbach tailing). The electroluminescence properties of the samples were also investigated. All samples showed room-temperature emission from the GaAsBi layers at wavelengths around 1.25 μm. The presence of localized states in the band gap was evident from taking electroluminescence measurements as a function of injection current and temperature.
Supervisor: David, John Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available