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This paper presents an extensive investigation of the impact of the resistivity of the silicon substrate on the vertical leakage and charge trapping in 200 V GaN-on-Si enhancement-mode high-electron mobility transistors. Three wafers having different substrate resistivities were submitted to combined DC characterization, step-stress experiments, and electroluminescence (EL) analysis. The results described within this paper demonstrate that: 1) the use of a highly resistive silicon substrate can increase the vertical breakdown voltage of the transistors, due to the fact that the voltage drop on the GaN buffer is mitigated by the partial depletion of the substrate (this latter causes a plateau region in the drain to substrate I–V characteristic) and 2) highly resistive substrate results in stronger trapping effects, due to the capacitance of the depleted substrate and the resulting backgating effects. The results described within this paper indicate that the choice of the resistivity of the substrate is the result of a tradeoff between high breakdown voltage (that could be in principle achieved through a highly resistive substrate) and the minimization of trapping processes (which can be hardly obtained with a resistive substrate). [ABSTRACT FROM AUTHOR]

This letter reports an in-depth study of the negative threshold voltage instability in GaN-on-Si metal-insulator–semiconductor high electron mobility transistors with partially recessed AlGaN. Based on a set of stress/recovery experiments carried out at several temperatures, we demonstrate that: 1) operation at high temperatures and negative gate bias (−10 V) may induce a significant negative threshold voltage shift, that is well correlated to a decrease in on-resistance; 2) this process has time constants in the range between 10–100 s, and is accelerated by temperature, with activation energy equal to 0.37 eV; and 3) the shift in threshold voltage is recoverable, with logarithmic kinetics. The negative shift in threshold voltage is ascribed to the depletion of trap states located at the SiN/AlGaN interface and/or in the gate insulator. [ABSTRACT FROM PUBLISHER]

This paper reports on an extensive analysis of the trapping processes and of the reliability of experimental AlGaN/GaN MIS-HEMTs, grown on silicon substrate. The study is based on combined pulsed characterization, transient investigation, breakdown, and reverse-bias stress tests, and provides the following, relevant, information: 1) the exposure to high gate-drain reverse-bias may result in a recoverable increase in the on-resistance (RON), and in a slight shift in threshold voltage; 2) devices with a longer gate-drain distance show a stronger increase in RON, compared to smaller devices; 3)current transient measurements indicate the existence of one trap level, with activation energy of 1.03 ± 0.09 eV; and 4) we demonstrate that through the improvement of the fabrication process, it is possible to design devices with negligible trapping. Furthermore, the degradation of the samples was studied by means of step-stress experiments in off-state. Results indicate that exposure to moderate-high reverse bias (<; 250 V for LGD = 2 μm) does not induce any measurable degradation, thus confirming the high reliability of the analyzed samples. A permanent degradation is detected only for very high reverse voltages (typically, VDS = 260-265 V, on a device with LGD = 2 μm stressed with VGS = - 8 V) and consists of a rapid increase in gate leakage current, followed by a catastrophic failure. EL measurements and microscopy investigation revealed that degradation occurs close to the gate, in proximity of the sharp edges of the drain contacts, i.e., in a region where the electric field is maximum. [ABSTRACT FROM AUTHOR]

Depletion mode insulated gate AlGaN/GaN power switching HEMTs were evaluated for stability under heavy-ion irradation. Experiments were performed for different types of heavy-ion species, values of gate bias, drain bias, and device geometry. For the insulated gate AlGaN/GaN devices, an as-of-yet unobserved single-event occurred, which we have termed single-event switching (SES). These SES events occurred next to previously observed single-event gate rupture (SEGR) events. It was found that the SES events were gate leakage dependent and stopped occurring above a certain threshold value of gate leakage. Statistical analysis showed that the cross section for single SES events exhibited a lognormal distribution with a median value close to the gate area, and the capture cross section exhibited a slight voltage dependence. The gate leakage after irradiation, on the other hand, was exponentially distributed and was strongly voltage and geometry dependent, indicating an electric field dependency. [ABSTRACT FROM AUTHOR]

III-Nitride materials are very promising to be used in next-generation high-frequency power switching applications. In this letter, we demonstrate the performance of normally off AlGaN/GaN/AlGaN double-heterostructure FETs (DHFETs) using a boost-converter circuit. The figures of merit of our large (57.6-mm gate width) GaN transistor are presented: RON \ast QG of 2.5 \Omega\cdot\nC is obtained at VDS = \140\ V. The switching performance of the GaN DHFET is studied in a dedicated high-frequency boost converter: both the switching times and power losses are characterized. We show converter efficiency values up to 96.1% at 500 kHz and 93.9% at 850 kHz at output power of 100 W. [ABSTRACT FROM AUTHOR]