Theoretical studies of GaInNAs for optoelectronic device applications

This thesis focuses on the theoretical analysis of GalnNAs alloys for use in optoelectronic devices. We develop reliable theoretical models that describe the properties of GaInNAs alloys and apply these to establish design rules. We develop a k·p model for the band structure of GaInNAs-based Quantum Wells (QW) that accounts for valence band mixing effects, strain effects and the N induced coupling of the conduction band states of GaInNAs alloys. We implement the model to study the effect of N on the conduction and valence bands. The optical properties of GaInNAs structures are studied and design rules that ensure optimal performance are derived for 1.3 μm emission. It is established that high N content decreases the differential gain and the Momentum Matrix Element (MME) for TE polarisation while it increases the transparency concentration and the MME for TM polarisation. The material gain and linewidth enhancement factor are found to have comparable values to InGaAsP structures. The effect of alternative barriers, namely GaNAs and GalnAs, is analysed and design maps are discussed. GaInNAs/GaNAs structures are predicted to provide better material gain characteristics than GaInNAs/GaAs, whereas we suggest the use of GalnAs barriers as a route for the equalisation of TE and TM of GalnNAs-based devices. We suggest and study the application of GaInNAs/GaAs QWs in Semiconductor Optical Amplifiers (SOA). It is concluded that N content deteriorates the SOA performance while polarisation insensitivity is not possible unless the GalnAs barrier is used. We investigate gain and nonlinear characteristics of GaInNAs-based Vertical Cavity Optical Amplifiers (VCSOA) and Vertical Cavity Amplifying Modulators (VCAM). The performance of GaInNAs-based VCSOAs is predicted to be comparable with InGaAsP-based VCSOAs. GaInNAs VCAMs exhibit good values of Extinction Ratio (ER) and we propose a scheme for the maximisation of ER when the VCAM is operated in the reflection mode. (author)