Naumov A. Features of lateral and vertical transport of electrons in quantum heterostructures based on group III nitrides

The work is related to electron transport in single- and double-barrier AlGaN/GaN quantum heterostructures (HS). Physical phenomena that occur in such HS in high electric and magnetic fields at cryogenic and room temperatures were experimentally studied to obtain the features of carriers' recombination and transfer. Also theoretical modeling of characteristics of HS was conducted for analysis and interpretation of experimental data. Studying a photoluminescence in doped and undoped HS, the effect of the PL spectral transformation was revealed: the band at 3.46-3.3 eV, associated with 2DEG electron-hole recombination, in modulation-doped HS has disappeared, instead, together with the enhanced band-edge PL at 3.49 eV, an intense band at 3.3-2.7 eV, attributed to recombination of donor-acceptor pairs with deep-level acceptor centers caused by the doping, has appeared. Studying a magnetotransport in HS with different quantum localization, all factors that affect the effective mass of two-dimensional electron gas were determined, and a refined value is deduced to be equal to (0.2±0.01)m0. In the study of a lateral transport in the HEMT-like HS, the effects of self-heating of the 2DEG channel and strong dependence on channel's size were demonstrated. In the study of a vertical transport in the RTD-like HS, a complex non-linear character of the tunneling caused by the interplay of internal and external built-in fields in the barriers and the QW was shown. The reasons of a current bistability associated with accumulation of charge carriers on interfacial and dislocation states, were determined. Possible ways to improve characteristics of HS were proposed.