Computational modelling of highly mis-matched alloys of GaNAsP and GaNAsBi as a laser gain material

The aim of this thesis work is to model and investigate the electronic band structure and current density of highly mismatched alloys of GaNAsP and GaNAsBi. To reveal the importance of these highly mismatched alloys we provide a comparison of GaNAsP and GaNAsBi with their nitrogen free N-counterpart. The GaP-based dilute nitride direct bandgap material Ga(NAsP) is gaining importance for the monolithic integration of laser diodes on Si microprocessors. The major advantage of this newly proposed novel laser material system is the small lattice mismatch between GaP and Si. However, from first gain measurements it is found that Ga(NAsP)/GaP material system has high threshold current at room temperature. Therefore, we present a comprehensive theoretical analysis of band alignment and threshold current in dilute nitride direct bandgap Ga(NAsP)/GaP/AlGaP QWs on silicon substrates using model calculations. The comparison of our calculated results with that of the experimental data indicates that the Auger effect involving CHCC process can be considered as the dominant non-radiative loss mechanism at 300K. It has just recently reported that highly mismatched semiconductor alloys of GaAs(1-x)Bi(x) has also several novel electronic properties, including a rapid reduction in energy gap with increasing x and also a strong increase in spin-orbit-splitting energy with increasing Bi composition. We, therefore to understand the origins of the rapid reduction in energy gap and its consequences, study and compare band gap and critical thickness of GaNAsBi. The results indicate that GaNAsBi material can be used in optoelectronic applications in the long wavelength region.