High-k perovskite gate oxide BaHfO3

Young Mo Kim,Useong Kim,Jae Hoon Kim,Namwook Kim,Chulkwon Park,Youjung Kim,Jaejun Yu,Kookrin Char,Taewoo Ha,Juyeon Shin

doi:10.1063/1.4974864

Abstract

We have investigated epitaxial BaHfO3 as a high-k perovskite dielectric. From x-ray diffraction measurement, we confirmed the epitaxial growth of BaHfO3 on BaSnO3 and MgO. We measured optical and dielectric properties of the BaHfO3 gate insulator; the optical bandgap, the dielectric constant, and the breakdown field. Furthermore, we fabricated a perovskite heterostructure field effect transistor using epitaxial BaHfO3 as a gate insulator and La-doped BaSnO3 as a channel layer on SrTiO3 substrate. To reduce the threading dislocations and enhance the electrical properties of the channel, an undoped BaSnO3 buffer layer was grown on SrTiO3 substrates before the channel layer deposition. The device exhibited a field effect mobility value of 52.7 cm2 V−1 s−1, a Ion/Ioff ratio higher than 107, and a subthreshold swing value of 0.80 V dec−1. We compare the device performances with those of other field effect transistors based on BaSnO3 channels and different gate oxides.

Highlights

High-k dielectric materials have been extensively investigated during the last decade to overcome the gate leakage problem of SiO2.1 The SiO2 layer thickness required for gate dielectrics nowadays is so thin (∼1 nm) that the leakage current would exceed 1 A cm2, causing unacceptably high power dissipation
Among various high-k materials, perovskite oxides such as SrTiO3 and BaTiO3 have been investigated as a gate oxide due to their high dielectric constant as well as their functional properties such as superconductivity, ferroelectricity, and ferromagnetism.[1,12,13,14,15,16]
Perovskite structure of BHO, in addition to the high dielectric constant, is advantageous, for various physical properties of other perovskite oxides which can be incorporated into a common crystal structure

Summary

Introduction

High-k dielectric materials have been extensively investigated during the last decade to overcome the gate leakage problem of SiO2.1 The SiO2 layer thickness required for gate dielectrics nowadays is so thin (∼1 nm) that the leakage current would exceed 1 A cm2, causing unacceptably high power dissipation. There exist a few reports regarding dielectric properties of BHO films that measured their dielectric constants as 23–45.20–23 to our knowledge, no field effect transistor (FET) using BHO as a gate insulator has been fabricated.

Results

Conclusion