Simulation of InSe for single photon emission application

The importance of photonic technologies is steadily growing in our daily lives. A new frontier of research is the development of non-classical light sources: sources that produce streams of photons with controllable quantum correlations. A central building block, in particular, is a single-photon emitter (SPE). Unlike classical light sources, SPEs are fundamental quantum devices for many scalable and leading technologies, such as quantum information and information, precision metrology and imaging. The ability to tailor and control quantum emitters, in order to realize efficient and scalable architectures, depends on site-selective defect engineering. In this work we have investigated the electronic properties of an InSe monolayer and its applicability as SPE. InSe is a layered compound consisting of several stacked InSe monolayers; each monolayer is composed by four atoms in the 2D unit cell. The single monolayer structure (2D phase) can be obtained through graphene-like exfoliation processes or by PVD and it is considered as one of the most promising materials for SPE applications for several reasons. Firstly, 2D InSe has a wide bandgap (around 2.9 eV) which can be tuned through the addition of substitutional impurities, moreover the two-dimensional nature of the monolayer allows for an easy modification of the crystal lattice with respect to bulk materials exploiting, for example, FIB, STP and SEM, or through the application of localized strains to the lattice. For these reasons one has the possibility to create SPE in a broad range of energies by employing 2D InSe. In this thesis work, we predict the electronic properties of InSe containing different substitutional impurities by using Density Functional Theory (DFT) simulations. For each system we calculate the formation energies, the band structure and the density of states. The best results to employ InSe as SPE are obtained for As, P, N and Ge substitutional impurities. In the last part of the work InGaSe alloys are studied through the combination of DFT and Cluster Expansion method, and their electronic properties predicted for different In/Ga fractions.