Yanchuk O. Electrical and photoelecrtical properties of the diodes structures based on indium and gallium monoselenides

The thesis is devoted to the creation of diode structures based on the indium and gallium monoselenides and to the investigation theirs fundamental electrical and photoelectrical properties as well as to the analysis of practical application possibilities. The peculiarity of present work is application of materials with wide spectrum of electro-physical parameters and creation on theirs base of the straightening structures different types (surface-barrier diodes, p-n-homo and heterojunctions). Mentioned factors in conjunction with variation of experiment conditions (voltage, temperature, level of illumination and its spectral composition etc.) allow us to extract from great number mechanisms of formation of the dark and the light characteristics the necessary mechanism and to investigate it in detail. The researches reveal that many mechanisms of current transmission implement in diode structures: heat and field-effect emission, generation-recombination processes in the area of space charge and impactionisation. It is established that the height of potential barrier of metal-semiconductor contacts is determined by the difference of photoelectric work functions of contacting materials during shielding action of surface levels. Its concentration changes in the limits (8-12)·1012 cm-2 and correlates with difference negative electron affinities of the elements of base compounds InSe and GaSe. For the first time energy band diagram of heterojunction pGaSe-nInSe that adequately explains all observed electrical and photoelectrical properties of diode structures is constructed. The type of diode structures and their parameters determine photoelectrical parameters and characteristics. It is established that impact ionization is mainly performed by the like-sign current carriers. The possibilities of practical application as photodetectors and devices of the type "scintillator-photodiode" and other devices are discussed.