Low Subthreshold Slope AlGaN/GaN MOS-HEMT with Spike-Annealed HfO2 Gate Dielectric.

Min Jae Yeom,Geonwook Yoo,Junseok Heo,Chan Ho Lee,Jeong Yong Yang,Roy Byung Kyu Chung

doi:10.3390/mi12121441

Abstract

AlGaN/GaN metal-oxide semiconductor high electron mobility transistors (MOS-HEMTs) with undoped ferroelectric HfO2 have been investigated. Annealing is often a critical step for improving the quality of as-deposited amorphous gate oxides. Thermal treatment of HfO2 gate dielectric, however, is known to degrade the oxide/nitride interface due to the formation of Ga-containing oxide. In this work, the undoped HfO2 gate dielectric was spike-annealed at 600 °C after the film was deposited by atomic layer deposition to improve the ferroelectricity without degrading the interface. As a result, the subthreshold slope of AlGaN/GaN MOS-HEMTs close to 60 mV/dec and on/off ratio>109 were achieved. These results suggest optimizing the HfO2/nitride interface can be a critical step towards a low-loss high-power switching device.

Highlights

III-Nitrides (InN, GaN, and AlN) are well-known for their intrinsic spontaneous polarization and piezo-electricity
It has been reported that HfO2 can be ferroelectric when doped with elements including Al, Gd, Si, Zr, etc
We investigated the impact of undoped HfO2 -based ferroelectric gate dielectric on the device performance of AlGaN/GaN HEMTs

Summary

Introduction

III-Nitrides (InN, GaN, and AlN) are well-known for their intrinsic spontaneous polarization and piezo-electricity. Owing to these excellent material properties, AlGaN/GaN-based HEMTs have been extensively studied and are being commercialized for high-frequency and highpower applications [1–3]. The effectiveness of a HfO2 -based ferroelectric gate for HEMTs remains somewhat elusive as the reported average values of SS were still relatively large (160–180 mV/dec). It has been reported the interface of HfO2 /GaN prone to the formation of unfavorable Ga–O bonds, which could potentially become interfacial traps [13]. AlGaN/GaN-based MOS-HEMTs with SS near 60 mV/dec and an on/off ratio of >109 have been demonstrated. A low SS value near 60 mV/dec could be achieved without compromising the overall performance of AlGaN/GaN MOS-HEMTs

Experimental

Results and Discussion

Conclusions