| In this thesis, we deal with the InGaAs/GaAs quantum dots and InGaN/GaN quantum systems. Both of the systems are under intensive study these days. Self-assembly growth of quantum dots on lattice mismatched substrate provides a promising way to realize zero-dimensional systems. The strain tensor in QDs is calculated and the spectrum via eight-band k· p is computed. Our results show several confined states in conduction band in agreement with experiments, while the simple single band method only has one bound state. The scattering mechanism in QDs are also studied. Thermalization through phonon processes is shown to be minimal, while electron-hole scattering is demonstrated to be an efficient way for carrier's thermalization within quantum dot. We also developed a set of equations for QD lasers. Within this framework, the threshold current density and multi-mode operation, as well as modulation of QD lasers are studied, which shows the general agreement with experiments.; III-nitride materials have extensive applications in the area of optoelectronics which covers the blue light region, solar-blind detectors and high-power devices. The presence of strong piezoelectric field and spontaneous polarization, as well as large material inhomogeneity make III-nitride semiconductor have new properties comparing with conventional III-V materials. In this thesis, the important InGaN/GaN quantum wells are studied by including these new effects. Our study shows that the photoluminescence in InGaN/GaN quantum well originates mainly from the band-band transition, while exciton is not important. The large Stokes shift is due to the strong piezoelectric field and effective quantum well width fluctuations. We demonstrate the existence of the linear electro-optic effect in this system. Finally, gain spectrum is calculated in InGaN/GaN quantum well laser and compared with published experiments. |
