Normally-off operation AlGaN/GaN MOS-HEMT with high threshold voltage

Abstract

Normally-off operation AlGaN/GaN high electron mobility transistors have been developed utilising a fluorine-based treatment technique combined with a metal-oxide-semiconductor gate architecture. Threshold voltage as high as 5.1 V was achieved by using an 16 nm-thick Al 2 O 3 gate oxide film. Additionally, the device performed a drain current density of 500 mA/mm and a peak transconductance of 100 mS/mm, which are comparable to the conventional normally-on devices.Introduction: AlGAN/GaN-based high electron mobility transistors are promising candidates for power electronic applications owing to their attractive properties, such as high breakdown field, high electron mobility, and capability of high temperature operation. For power switching applications, devices with normally-off operation are necessary because they can not only help simplify the complexity of the circuit but also reduce standby power consumption. In addition, they provide a fail-safe function because a noise higher than 3 V may occur on the gate electrode during the device operation [1]. Several approaches towards such requirements based on an AlGaN/GaN heterostructure have been investigated, such as the recessed gate [2], fluoride-based treatment [3], and the band diagram engineered approach [4,5]. However, these approaches still encounter an issue which is either lower current density or insufficient threshold voltage for the gate noise blocking. In this Letter, we combined the fluorine-based treatment technique and an Al 2 O 3 film as the gate oxide layer to demonstrate normally-off operation AlGaN/GaN MOS-HEMTs with high threshold voltage, and with comparable current density to conventional normally-on HEMTs

An E-Mode p-Channel GaN MOSHFET for a CMOS Compatible PMIC

“…Achieving E-mode operation in GaN is challenging because the polarization induced 2DEG or 2DHG first needs to be depleted at zero gate voltage. In n-channel GaN HFETs or MOSHFETs, various techniques to implement E-mode behaviour are recessed gate [8]- [10], or ion implantation [11]- [13]: both methods can be employed on a PSJ platform. On the other hand, less attention has been paid to p-channel devices due to the low mobility of holes in GaN ( at room temperature [14]), which leads to poor on-current and switching speed.…”

Oxide interfacial charge engineering towards normally-off AlN/GaN MOSHEMT

“…only 1.5 nm [15]. For power electronics applications normally-off operation is required to simplify the design of the driving circuit by eliminating the requirement of negative voltage supply and to reduce the switching [16] and off-state standby power loss [17].…”

Effect of GaN surface treatment on Al2O3/n-GaN MOS capacitors

“…3 Al 2 O 3 /GaN structures are being incorporated into normally off high-voltage power switching devices. 4,5 Finding a suitable gate oxide is essential to fabricate GaN-based MOS devices with outstanding performance. In selecting the gate oxide, a band offset larger than 1 eV is needed to suppress leakage currents.…”