| This thesis is divided into two parts. First, the effect of a systematic variation of the indium and nitrogen concentrations in InGaAsN/GaAs multiple quantum wells is studied by x-ray diffraction, low temperature transmittance and room temperature photoreflectance spectroscopy. The effect of nitrogen incorporation on the valence band configuration can be explained by the strain variation. The unstrained valence band alignment is found to be unchanged if constant valence band effective masses, deformation potentials and elastic constants are assumed. A transition involving the second confined conduction band energy level is observed in tensile-strained GaAsN/GaAs quantum wells even if the light hole band quantum well is likely to be too shallow to allow the formation of a second confined state. The interband optical transition parity rule may not apply in this case due to the weak confinement of the valence states. The incorporation of a nitrogen fraction around 1% leads to a moderate increase of the electron effective mass (Deltam*e ∼ 0.03 m0) in structures with and without indium. The bandgap redshift due to a 1.5% nitrogen concentration decreases by as much as 30% when the indium concentration increases from 0% to 20%. This suggests that the interaction between the nitrogen impurity level and the conduction bands decreases as the indium composition increases.;In the second part of the thesis, the potential of the new material system for photodetector applications is investigated. The first resonant cavity-enhanced InGaAsN photodetector is demonstrated; it has an operating wavelength near 1.3 mum and a quantum efficiency of 72%. Even though nitrogen incorporation reduces material quality, the increase of the dark current in p-i-n multi-quantum well structures is tolerable. Finally, the first InGaAsN heterojunction phototransistor is demonstrated experimentally. |
