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In GaN Schottky barrier diodes (SBD), there is a trade-off between the turn-on voltage and the leakage current. In this study, recess-free 4 nm-thin-barrier AlGaN/GaN SBDs with minimal leakage current as well as excellent turn-on voltage homogeneity are developed, which enable better electrical control to pinch off the 2DEG channel under the anode region and avoids trap introduced in the barrier etching process. In detail, the effect of reverse stress on the SBD performance is initially explored by using differential conductance, and then, the anode-to-cathode distances and temperatures dependence of SBDs output characteristics are systematically studied. The fabricated thin-barrier GaN SBDs show a turn-on voltage of ∼0.75 V and a low level leakage current of 9.66 × 10−10 (1.91 × 10−8) A/mm at 300 (423) K, which is among the lowest reported values at the comparable reverse bias voltage and temperature. Moreover, structure parameters of the thin-barrier AlGaN/GaN SBD are systematically modeled and optimized by the TCAD simulations, including anode metal work function, Al mole fraction, the anode-to-cathode distance, and slanted anode angle. The introduction of slanted anode is found to have significant effect on the improvement of reverse breakdown voltage and leakage current characteristics. [ABSTRACT FROM AUTHOR]

The superjunction MOSFET power devices, such as p-n column superjunction (named SJ or CoolMOS) devices and oxide-bypassed (OB) devices, are highly recognized for their higher blocking capability and lower on-state resistance. However, the performance of SJ devices is greatly handicapped due to difficulties in formation of perfect charge-balanced SJ p-n columns by the current process technology, especially for devices with small widths and voltage ratings below 180 V. OB devices can be an alternative in this voltage region, which utilize the well established oxide thickness control in fabrication instead of the difficult doping control as in SJ devices. However, OB drift region electric field distribution is not as optimal as that in SJ devices. Gradient oxide-bypassed (GOB) structure enhances the performance of OB devices so that it can achieve a performance comparable to that of an ideal p-n column SJ device in the medium voltage range, and at the same time, requires simple process technology. Complete descriptions on the GOB device and related design issues are presented in this paper. Fabrication issues are also discussed with possible sacrificial materials and etchants for making the vertical graded oxide sidewalls. Design cases for 80, 120, and 180 V GOB devices are also illustrated for better understanding in the device. [ABSTRACT FROM AUTHOR]

The performance of specific on-state resistance (Ron,sp) versus breakdown voltage (Vbr) of a superjunction power MOSFET device is constrained by the quality of its sidewall junctions formed by neighbouring p and n columns in the drift region. The p–n junction quality, which is inevitably affected by the inter-column dopant diffusion in practice, will limit the Ron,sp–Vbr device performance if no compensation measure is taken. A detailed study of the influence of sidewall junction quality on performance at various column widths under given thermal process conditions was carried out through process and device simulations. The study discovers the practical optimal performance of superjunction (SJ) DMOS and UMOS structures under the influence of dopant inter-column diffusion. Analysis of the phenomenon shows that the degradation of the breakdown voltage is caused by the p and n column charge imbalance. Practical SJ performance equations, which model the influence reasonably well, are derived in the paper. These equations can be used to predict the practical performance of an SJ device under given thermal conditions, which in turn guides us to the compensation measures required to achieve better performance. [ABSTRACT FROM AUTHOR]