Vacancies and Their Complexes in Nitride Semiconductors

Vacancies are point defects representing a missing atom in the crystal lattice. They are very important crystal defects in any semiconductors, which significantly influence their properties. Although nitride semiconductors are widely industrially used and became the second most important semiconductor after silicon, there is a significant lack of knowledge about these defects in nitrides. In the cooperation with Department of Low Temperature Physics MFF UK we try to find relation between the concentration of group III vacancies and particular technological parameters for MOVPE grown GaN, InGaN and AlGaN layers and to define technological conditions which enhance cluster formation or formation of gallium vacancy complexes with other native point defects. The main characterization method for group III vacancy is positron annihilation spectroscopy. Understanding of the relation between technological parameters of nitride epitaxy, V_Ga concentration and clustering is extremely important for all nitride MOVPE technologists. Identified vacancies, complexes and clusters help us experimentally define the effect of particular native point defects, on nitride heterostructure properties. Results of this work should help to improve the understanding of processes in nitride semiconductors and improve technology of their preparation