This paper presents an extensive investigation of the properties of the trap with activation energy equal to 0.6 eV, which has been demonstrated to be responsible for current collapse (CC) in AlGaN/GaN HEMTs. The study was carried out on AlGaN/GaN HEMTs with increasing concentration of iron doping in the buffer. Based on pulsed characterization and drain current transient measurements, we demonstrate that for the samples under investigation: 1) increasing concentrations of Fe-doping in the buffer may induce a strong CC, which is related to the existence of a trap level located 0.63 eV below the conduction band energy and 2) this trap is physically located in the buffer layer, and is not related to the iron atoms but—more likely—to an intrinsic defect whose concentration depends on buffer doping. Moreover, we demonstrate that this level can be filled both under OFF-state conditions (by gate-leakage current) and under ON-state operation (when hot electrons can be injected to the buffer): for these reasons, it can significantly affect the switching properties of AlGaN/GaN HEMTs

Comprehensive RF stress-test campaign has been performed over AlGaN/GaN high-electron mobility transistor employing different GaN buffer designs, including unintentional doping, carbon doping and iron doping. No signature of gate-edge degradation has been found, and good correlation emerges between the buffer composition, subthreshold leakage current, and permanent degradation of the RF performance. The degradation mechanism, more pronounced in devices with parasitic buffer conductivity, involves the generation of additional deep trap states, the worsening of the dynamic current collapse, and the subsequent degradation of RF output power

The aim of this work is to quantitatively investigate the influence of buffer doping on the current collapse of AlGaN/GaN HEMTs, and to analyze the contribution of trap states to the increase in current collapse detected after reverse-bias stress. The study was carried out on GaN-based HEMTs with increasing levels of iron doping in the buffer, which were submitted to drain current transient measurements and reverse-bias stress. Results demonstrate that the use of Fe-doping may significantly impact on current collapse; moreover, we demonstrate that the increase in current collapse detected after reverse-bias stress is not due to the generation of new types of defect, but to the increase in the signal of the defects which were already present before stress

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Today microwave market has identified GaN-HEMT technology as a strategic enabling technology for next generation MMICs to be implemented in high performance RF sub-assemblies such as T/R Modules, Solid State Power Transmitters, Compact Receivers, High Speed Communications. To allow commercial market entry of GaN technology, a tradeoff between high RF performance and low cost is mandatory and a possible solution is represented by GaN-on-Silicon substrate. In this scenario the evaluation of FETs RF performance and losses of passive components are demanding to understand the feasibility of GaN MMIC on Si. Following such approach, in SELEX Sistemi Integrati a 4 inches GaN-on-Si wafer containing discrete active devices and passive components has been fabricated with the 50μm Si thickness. RF FETs performance demonstrates an output power of 4W/mm @ 3GHz, while passive components characterization exhibits similar behavior of GaN SiC passive elements up to C Band.