Electronic and optical properties of semiconductor quantum wells and dots
The influence of structural size and geometry on the electronic states, optical transitions and nonlinear optical response in semiconductor quantum wells and dots has been investigated. A quantum mechanical theory of optical nonlinearities in semiconductors has been used in conjunction with the empirical pseudopotential band structure method to determine the structural parameters leading to optimum second harmonic generation in p-type asymmetric GaAs/AlxGa₁₋xAs quantum well structures. Maximum confinement of all participating states is of paramount importance for optimising such responses. The multi-band effective mass approximation was adapted for the calculation of the electronic structure and optical transitions in cubic GaAs/AlAs quantum dots and in the recently discovered InAs/GaAs self-assembled structures. The calculation revealed the importance of factors such as the quantum mechanical mixing between bulk basis states, inhomogeneous strain and symmetry in the construction of the optical signatures of these dots.