Band-offset ratio calculations of nitrogen containing III-V quantum wells

2fc^, ABSTRACT BAND-OFFSET RATIO CALCULATIONS OF NITROGEN CONTAINING III-V QUANTUM WELLS KOÇAK, Fatma M. Sc, Engineering Physics Department Supervisor: Assoc. Prof. Dr. Beşire GÖNÜL September 2003, 58 Pages A comparative study of the band-offset ratio of the three competing laser materials, namely InGaAsP-InP, AlGalnAs-InP, and GalnNAs-GaAs has been undertaken. Our theoretical study shows that model solid theory can be used to calculate the band offset ratios of the GalnNAs-GaAs for small nitrogen concentration including the effect of strain and modifications in conduction band but neglecting the direct effect of nitrogen. We have calculated that the alternative AlGalnAs and GalnNAs laser systems have substantially better band alignment than the commonly used InGaAsP. Strain compensation brings further benefits to that of the three competing laser systems. Therefore, high temperature operation has been anticipated in these alternative material systems with strain compensated barriers due to better electron and hole confinement as a result of the increased band offset and a more favourable band offset ratio. Our theoretical calculations indicate a significant increase in conduction band offset ratio and a decrease in valence band offset ratio with the introduction of nitrogen to InGaAs. This result highlights the intrinsic superiority of the N-based laser system. Keywords: III-V Semiconductors, Nitrides, Quantum Well Lasers, Band-offset ratios, Band alignments. iii