6 - Quantum Dots of Indium Nitrides

Abstract

Sever small, non-stoichiometric InAsN and InN atomic clusters have been optimized using computational methods based on the first-principle, quantum many body-theoretical approaches described in Chapter 2 to obtain two groups of 14 atomic molecules composed of In, As and N atoms. The structure of the clusters has been derived from that of the pyramidal and prismatic symmetry elements of the zincblende InAs (the pre-designed In10As4 pyramid of Chapter 3) and wurtzite InN bulk lattices. Electronic and magnetic properties of such small, non-stoichiometric systems of about 1 nm in linear dimensions differ dramatically from those of their bulk counterparts. In particular, in nanoscale structures tetrahedral or hexagonal symmetry is broken due to substitution doping of In-As QDs with nitrogen, finite size and quantum confinement effects, thus allowing for excitations optically forbidden in the parent bulk zincblende or wurtzite structures. Results of the studies discussed in this chapter indicate that nitrogen doping significantly enhances stability of the optimized fcc-derived QDs, and both doping and quantum confinement effects are instrumental in manipulating the optical transition energy of the clusters in a wide range of values from ultraviolet to infrared. These results are in good agreement with available experimental data, and provide a fundamental basis for explanation of experimentally observed properties of both low dimensional and bulk indium nitride systems actively studied at present.