Quantum confined electronic states in InGaN dots embedded in GaN: tight-binding calculation

We have calculated the electronic states of In_0.2Ga_0.8N hexagonal quantum dots (QDs) embedded in a GaN barrier layer using a valence-force-field method and an sp³ tight-binding method. Assuming no polarization field, the energy gap is calculated to be 2.710 eV for the QD with diameter of 86.4 Å and height of 20.8 Å. The electron wave functions confined in the QD exhibit atomic scale fluctuation due to the alloy disorder. Including the piezoelectric polarization, we have found that the nonuniform polarization field is induced in the QD; 2.51 MV/cm at the dot center. Under the field, the energy gap is 2.502 eV (decreases by 0.208 eV). The energy separation between the ground and next excited levels of electron is 63.6 meV, which is large enough for application to the QD laser