In this paper we have investigated the relationship between off-state breakdown voltage and gate-to-drain distance (Lgd) for AlGaN/GaN HEMTs fabricated on a free-standing GaN substrate. The off-state ...breakdown voltage exhibited a linear increase up to Lgd of around 80 μm but saturated at about 4000 V when Lgd > 80 μm. Therefore, we proposed that when Lgd <; 80 μm, the breakdown voltage of HEMTs was dominated by leakage current under the channel and when Lgd > 80 μm, it was determined by the leakage current outside of the channel.
This report describes the fabrication and characteristics of GaN p–n junction diodes on free‐standing GaN substrates with low dislocation density. We have demonstrated GaN p–n junction diodes with a ...unique field‐plate (FP) structure. The breakdown voltage VB is further improved due to the FP structure and the low dislocation density. The breakdown voltage of a diode of 60 µm in diameter with the FP structure is over −1000 V, and the leakage current is below 10−9 A until reaching the breakdown voltage. Even in larger diodes (100 and 200 µm in diameter) with FP, the breakdown voltage is over −800 V. However, the specific on‐resistance Ron is high due to damage by the plasma process of sputtering. The specific on‐resistance is further improved due to using a low damage passivation film. As a result, a specific on‐resistance of 1.2 mΩ · cm2 is obtained.
We report on the validity of using a C‐doped GaN buffer to achieve high‐breakdown‐voltage AlGaN/GaN high‐electron mobility transistors (HEMTs) on conductive free‐standing GaN substrates. We use ...trimethygallium to dope C into the buffer. We show that breakdown voltage depends not only on the C concentration of the buffer but also on the surface morphology of the HEMT structure. We demonstrate off‐state breakdown voltage of over 2 kV by controlling the C concentration of the buffer, thickness of the buffer, and the surface morphology.
In this work, we study the breakdown electric field and resistivity of Fe-doped semi-insulating GaN substrates with various Fe doping concentrations. The substrate with Fe doping concentration of ...4×10 20 cm −3 exhibited an effective lateral breakdown field of 2 MV/cm with a resistivity of more than 10 12 Ωcm. It was found that increasing the Fe concentration was effective to enhance the resistivity and effective lateral breakdown electric field.
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