Low-Loss and High-Voltage III-Nitride Transistors for Power Switching Applications

Abstract

This paper describes recent technological advances on III-nitride-based transistors for power switching applications. Focuses are placed on the progress toward enhancing the breakdown voltage, lowering the ON -resistance, suppressing current collapse, and reducing the leakage current in AlGaN/GaN high-electron mobility transistors (HEMTs). Recent publications revealed that the tradeoff relation between ON -resistance and breakdown voltage in AlGaN/GaN HEMTs exceeded the SiC limit and was getting close to the GaN limit; however, the breakdown voltage achieved was still lower than the theoretical impact ionization limit. A novel process featuring strain-controlled annealing with a metal stack, including Al gave rise to significant reduction in the sheet resistance in AlGaN/GaN heterostructures, suggesting the possibility of dramatic reduction in ON -resistance of GaN-based power devices. Some of the interesting approaches to suppress current collapse indicated that surface trapping effects must be controlled by the optimization of surface processing as well as by the reduction of bulk traps in the epitaxial layers. Close correlation between the local gate leakage current and point defects exposed on the free-standing GaN substrate demonstrated that further reduction of defects on bulk GaN substrates is truly required as future challenges

TMAH-based wet surface pre-treatment for reduction of leakage current in AlGaN/GaN MIS-HEMTs

“…AlGaN/GaN-based metal-insulator-semiconductor highelectron mobility transistors (MIS-HEMTs) have been studied for high frequency and high power applications, owing to outstanding material properties of III-nitrides such as a high electron mobility, a high electron saturation velocity, and a high breakdown electric field [1][2][3][4][5].…”

Breakdown degradation of AlGaN/GaN HEMTs with multi-finger gate patterns

“…AlGaN/GaN HEMTs are promising for low-loss and high-voltage power switching applications [1]. However, for application in actual power supply circuits, it is necessary to have high current and high breakdown voltage (V br ) capability.…”

Highly reduced current collapse in AlGaN/GaN high-electron-mobility transistors by combined application of oxygen plasma treatment and field plate structures

“…[1][2][3][4][5] However, GaN-based devices are still hounded by several problematic issues, foremost of which is the well-known current collapse. It is widely believed that current collapse is predominantly, if not exclusively, due to charging of traps on the AlGaN surface.…”