Influence of Overheating Effect on Transport Properties of AlGaN/GaN Heterostructures

摘要

We report on peculiarities observed in electrical characteristics of AlGaN/GaN transmission line model (TLM) devices. Special attention is given to self-heating processes and thermal effects in Al{sub}xGa{sub}(1-x)N/GaN based devices. The set of the samples under test contains conventional Al{sub}33Ga{sub}67N/GaN heterostructure with 1μm thick buffer on a sapphire substrate and wafers which differ from the conventional one by a layer (SiC substrate, additional AlN spacer, Al mole fraction of the barrier). The Al{sub}30Ga{sub}70N/GaN structures with 3μm buffer grown on thin (450μm) and thick (3mm) sapphire substrate investigated as well. Comprehensive analysis of the experimental data (current-voltage characteristics, noise figures) combined with the simulation of the thermal budget of the devices reveals strong dependence of device performance and overheating not only on substrate type but also on buffer thickness as well as Al mole fraction of barrier layer. Regarding this the optimal conditions for observation of hot-electron effects can be determined. The obtained results can be used as guidelines in optimization of wafer and device design in order to reach the best performance frequently predicted for nitride based structures.