Enhancement of Two-Dimensional Electron-Gas Properties by Zn Polar ZnMgO/MgO/ZnO Structure Grown by Radical-Source Laser Molecular Beam Epitaxy

Li Meng,Jingwen Zhang,Xun Hou,Qun Li

doi:10.1155/2015/694234

Abstract

A Zn polar ZnMgO/MgO/ZnO structure with low Mg compositionZn1-xMgxOlayer (x= 0.05) grown on a-plane (11–20) sapphire by radical-source laser molecular beam epitaxy was reported. The insertion of a thin (1 nm) MgO layer between ZnMgO and ZnO layers in the ZnMgO/ZnO 2DEG structures results in an increase of 2DEG sheet density and affects electron mobility slightly. The carrier concentration reached a value as high as 1.1 × 1013 cm−2, which was confirmed byC-Vmeasurements. A high Hall mobility of 3090 cm2/Vs at 10 K and 332 cm2/Vs at RT was observed from Zn0.95Mg0.05O/MgO/ZnO heterostructure. The choice of the thickness of MgO was discussed. The dependence of carrier sheet density of 2DEG on ZnMgO layer thickness was calculated in theory and the theoretical prediction and experimental results agreed well.

Highlights

ZnO and its heterostructures, which have several advantages including a high saturation velocity [1], a large conduction band offset for ZnMgO/ZnO heterostructures [2], and the possibility to form a high-density two-dimensional electron-gas (2DEG) [3], have great potential for highfrequency and high-power device applications
The formation of 2DEG at Zn polar Zn1−xMgxO/ZnO interface has been observed by a few groups using molecular beam epitaxy (MBE) [4,5,6,7,8], pulse laser deposition (PLD) techniques [9], metal-organic vapor phase epitaxy (MOVPE) [10], and RF sputtering [11]
We report a Zn polar ZnMgO/MgO/ZnO structure to enhance twodimensional electron-gas properties and discuss the dependence of carrier sheet density of 2DEG on ZnMgO layer thickness which was calculated in theory and the theoretical prediction and experimental results agreed well

Summary

Introduction

ZnO and its heterostructures, which have several advantages including a high saturation velocity [1], a large conduction band offset for ZnMgO/ZnO heterostructures [2], and the possibility to form a high-density two-dimensional electron-gas (2DEG) [3], have great potential for highfrequency and high-power device applications. It has been reported that modified AlGaN/AlN/GaN structures, which employ a thin AlN interfacial layer between AlGaN and GaN layers, show higher 2DEG properties than those of conventional AlGaN/GaN structures. This is reported to be a result of the reduction of alloy disorder scattering due to the suppression of carrier penetration from the GaN channel into the AlGaN layer [14,15,16,17]. We report a Zn polar ZnMgO/MgO/ZnO structure to enhance twodimensional electron-gas properties and discuss the dependence of carrier sheet density of 2DEG on ZnMgO layer thickness which was calculated in theory and the theoretical prediction and experimental results agreed well

Methods

Results

Conclusion