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Title: Characterisation of InGaAsP heterojunction photodetectors
Author: Thompson, D. M.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1994
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In this work the operation of InGa AsP/InP/InlAs photodetector devices, designed to be implemented in photoelectronic circuits (OEICs), are considered. A numerical simulator has been adapted for the analysis of these structures. The heterogeneous nature of the problem is taken into account using the band parameter scheme with suitable physical models. Initially the numerical simulator is used to examine and characterise a 2-D heterojunction PIN (HPIN) detector. The modelling of a more complex heterojunction integrable detector called a heterojunction field effect transistor photodetector (HFETPD) is then investigated. The device has a fabrication methodology that is compatible with a range of components used in photoelectronic integration and promises low noise, high speed operation with the prospect of avalanche gain. A 1-D analytical model of the gate-substrate potential profile of the the HFETPD in equilibrium and with a gate bias is presented. The analytical results are shown to be in excellent agreement with the numerical simulator. The primary aim of the analysis is the determination of the depletion width in the active layer of the device for an arbitrary doping profile. Quantifying the active layer depletion width is necessary when estimating the speed of response of the detector. The current flow over the gate-substrate heterojunction will occur via thermionic emission and this process is included in the numerical simulator by using thermionic emission as a boundary condition. The numerical results are then verified using the standard 1-D analytical thermionic emission current model combined with the gate-substrate potential model. The effect of degeneracy in the device is also considered because the inclusion of Fermi-Dirac statistics is important when modelling modern devices, particularly heterostructures. The numerical simulator is applied to the 2-D HFETPD and is used to investigate its non-illuminated and illuminated behaviour. The results are used to examine the validity of the 1-D analytical models developed, when dealing with a 2-D structure.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available