Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618809
Title: GaInAsSbP alloys for mid-infrared optoelectronic devices
Author: Cheetham , Kieran James
Awarding Body: Lancaster University
Current Institution: Lancaster University
Date of Award: 2011
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Abstract:
The GaInAsSbP pentanary system has been utilised to grow epilayers on InAs substrates using Liquid Phase Epitaxy, and used to form the basis of. optoelectronic devices in the technologically important Mm spectral range (3-5 μm). The photoluminescence spectra of a single epilayer confirmed that the dominant radiative recombination mechanism was band-to-band in the pentanary layer. XRD analysis indicated the epilayers did not suffer from spinodal decomposition, and SEM and SIMS confirmed the layers were flat and abrupt. Raman spectroscopy was carried out over a wide range of lattice-matched InAsSbP compositions for the first time, before a further study on GaInAsSbP. Binary-like optical phonon signals were identified, and their position was found to directly relate to the composition of the alloy. Phonon signals resulting from alloy disorder were identified in the Raman spectra, which provides a valuable tool for future work on determining crystal quality. Prototype mesa diode devices were fabricated using wet etching with the addition of an InAsSbP window layer. Uncooled photodetectors were found to operate at room temperature, limited by diffusion current. Thermophotovoltaic cells using the same structure, designed for use with comparatively low temperature heat sources, were found to have a 33% fill factor. This is the first report of a pentanary alloy used for such an application. The corresponding photoresponse spectra exhibited two peaks, attributed to recombination in both the window layer and active region. Room temperature LEDs were demonstrated, operating with a 50% duty cycle, with their emission peaking at ~3.75 μm. The analysis of the excitation dependent electroluminescence allowed the electron effective mass of 0.018 mo to be calculated for the GaInAsSbP alloy. The devices were found to be limited by CHCC Auger recombination, even though the CHSH mechanism was suppressed by increasing the spin-orbit split-off band, as confirmed by high pressure measurements. The bandgap dependence of GalnAsSbP on pressure was found to be 10.7 meV/khar, which is believed to be the first such investigation for a III-v pentanary alloy. Multi-ring structures v/ere fabricated and current crowding effects were investigated. It was found that by employing multiple rings, rather than spot contacts, there was an improvement in the current spreading. and hence the output of the device. When only the outer-most contact was energised the current crowding under the contact was sufficient to facilitate whispering gallery modes. Lasing was achieved at 4K with drive currents of >300 mA, peaking at 3.3 μm.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.618809  DOI: Not available
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