Mechanical and Optoelectronic Properties of InGaN Self-Assembled Quantum Dots

In this work, we investigate the variation of electronic structures of self-assembled InGaN/GaN quantum dots (QDs) due to (a) indium distribution within QDs; (b) piezoelectric constant e15; (c) QD structures; and (d) nonlocal theory in strain. Strain and piezoelectric fields, single-particle state energies and wave functions of the QDs are all estimated by a commercial finite element package—COMSOL, with the aid of theory of piezoelectricity and a k•p Hamiltonian.
Based on simulation results, electron (hole) energy for QDs with ellipsoid (linear) indium distribution has similar behavior to those with uniform indium distribution. On the other hand, the Coulomb interactions of these three indium distributions are not significantly different. We find also that, on optical properties of QDs, piezoelectric constant e15 cannot be neglected. Since piezoelectric potential will be underestimated by an amount of 142 mV (from 766 down to 624 mV) by neglecting e15, and hence leading to an overestimation in transition energy. Moreover, this discrepancy will increase with the size of QDs increase.
In the third part of this thesis, we find that the transition energies of the QDs are able to be promoted about 53 meV by inserting QDs in between two quantum wells (QWs). And QWs play critical roles in changing the piezoelectric potential and the Coulomb interaction of QDs. In the fourth part, we find that, by introducing nonlocal theory in strain, the strain and piezoelectric potential decrease significantly. Consequently, the nonlocal elasticity theory has a great impact on the electron and hole ground-state energies.