Energy levels of nitride quantum dots: Wurtzite versus zinc-blende structure

Nitride based III-V quantum dots (QD's) GaN, InN, and AlN have been investigated theoretically using the hole effective mass Hamiltonian derived by the (k) over right arrow.(p) over right arrow method. The nitride based QD's have significantly different properties compared to II-VI based QD's and also other III-V based QD's such as GaAs and InP. III-V based nitrides can have both zinc blende and wurtzite crystal structures whereas GaAs and other III-V and II-VI QD's exist only in the zinc blende structure. The study of nitride QD's therefore offers an unique opportunity of studying the role of the crystal field which is present in the wurtzite structure and is absent in zinc blende structure. The energies and the eigenfunctions for spherical quantum dots have been calculated as functions of the dot radius R for both zinc blende and wurtzite structures for both the zero spin orbit coupling (SOC) and finite SOC. For low lying states, in the zero SOC limit, the energies have a 1/R-2 dependence at all R for zinc blende structures but the presence of crystal field in wurtzite modifies the 1/R-2 dependence at intermediate R but not in small and large R. The addition of SOC further modifies the behavior at large R and the energies vary more slowly than 1/R-2 for both the zinc blende and wurtzite structures. For very high excited states of large QD's, the wurtzite pattern approaches that of the zinc blende.