Results of the first ab initio simulations of InN/GaN multiquantum well (MQW) system are presented. The DFT results confirm the presence of the polarization charge at InN/GaN interfaces, i.e. at polar InN/GaN heterostructures. These results show the potential jumps which is related to the presence of dipole layer at these interfaces. An electrostatic polarization analysis shows that the energy minimum condition can be used to obtain the field in InN/GaN system, employing standard polarization parameters. DFT results are in good agreement with polarization data confirming the existence of electric field leading to separation of electron and holes in QWs and emergence of Quantum Confined Stark Effect (QCSE).
It is shown that charge transfer, the process analogous to formation of semiconductor p-n junction, contributes significantly to adsorption energy at semiconductor surfaces. For the processes without the charge transfer, such as molecular adsorption of closed shell systems, the adsorption energy is determined by the bonding only. In the case involving charge transfer, such as open shell systems like metal atoms or the dissociating molecules, the energy attains different value for the Fermi level differently pinned. The Density Functional Theory (DFT) simulation of species adsorption at different surfaces, such as SiC(0001) or GaN(0001) confirms these predictions: the molecular adsorption is independent on the coverage, while the dissociative process adsorption energy varies by several electronvolts.
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