A large gate metal height technique is proposed to enhance breakdown voltage in GaN channel and AlGaN channel high-electron-mobility-transistors (HEMTs). For GaN channel HEMTs with gate–drain spacing L
GD = 2.5 μm, the breakdown voltage V
BR increases from 518 V to 582 V by increasing gate metal height h from 0.2 μm to 0.4 μm. For GaN channel HEMTs with L
GD = 7 μm, V
BR increases from 953 V to 1310 V by increasing h from 0.8 μm to 1.6 μm. The breakdown voltage enhancement results from the increase of the gate sidewall capacitance and depletion region extension. For Al0.4Ga0.6N channel HEMT with L
GD = 7 μm, V
BR increases from 1535 V to 1763 V by increasing h from 0.8 μm to 1.6 μm, resulting in a high average breakdown electric field of 2.51 MV/cm. Simulation and analysis indicate that the high gate metal height is an effective method to enhance breakdown voltage in GaN-based HEMTs, and this method can be utilized in all the lateral semiconductor devices.
A focused microwave power transmission (MPT) system with high‐efficiency rectifying surface is proposed. This work has two main novel contributions: (i) most of wireless power transmission systems reported so far are non‐focused. This study presents the first focused MPT system with circular polarisation; (ii) a novel high‐efficiency rectifying surface using sub‐wavelength resonant elements is developed. To design a focused transmitting array antenna with high power density at the receiving site and high beam collecting efficiency in the near field, a method based on the optimisation of a partial scattering matrix is employed. A left‐handed circularly polarised microwave power rectifying surface consisting of 8 × 8 sub‐wavelength resonant elements is designed and the measured conversion efficiency reaches 57.74%. To validate the concept, an experimental system including one focused transmitting array antenna and one 2 × 2 elements rectifying surface is implemented and measured, and the improvement of output direct current (DC) power and radiofrequency (RF)‐to‐DC conversion efficiency compared with non‐focused condition is shown. The highest RF‐to‐DC efficiency of 66.5% is achieved in the focused mode, compared to that of 34.8% only in the non‐focused mode as in traditional systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.