The electron field and photo-field emission from GaN nanostructures has been analyzed in this review. In order to explain the obtained experimental results, a model was proposed taking into account the change in carrier concentration distribution in the main and the satellite valley during the emission process. The lowering of work function (due to the increased number of carriers in the satellite valley) can explain the decrease in the Fowler-Nordheim plot slope. It was shown that the energy difference between the main and satellite valley in GaN was decreased in the case of quantum confinement, thus increasing the probability of electron transition from Γ to X valley at same electric fields.

Investigations of electron photo-field emission demonstrated that the Fowler–Nordheim plots of the emission current have different slopes for nonilluminated and illuminated devices. A model based on the electron emission from valleys having different specific electron affinities is proposed to explain the experimental results. In the absence of illumination the emission takes place only from the lower valley. Upon UV illumination and presence of a high electric field at the emitter tip, the upper valley of the conduction band appears to be occupied by electrons generated at the valence band.

A description of the status of the art of experimental and theoretical investigations of local crystalline structures of tetrahedron ordered ternary and quaternary semiconducting alloys is presented. Experimental EXAFS data and FTIR analysis are summarized and analyzed using both the Rigid Network Cations theoretical model and the Strained-tetrahedra model. Internal preferences of ion pairs in ternary and quaternary alloys are discussed. Several ternary systems of different structures show ideal quasi-canonical Bernoulli distributions, while others are characterized by extreme preferences in which one, several or even all configurations are depressed or even lacking. The results demonstrate that the validity of the Bernoulli distribution is limited and not fulfilled in many systems. This article is an expanded version of the scientific reports presented at the International Conference on Semiconductor Nanostructures for Optoelectronics and Biosensors 2016 ICSeNOB2016, May 22–25, 2016, Rzeszow, Poland.