Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations.

H.-P. Lee,L. D. Rosario,C. Bayram,J. Perozek

doi:10.1038/srep37588

H.-P. Lee, L. D. Rosario + Show 2 more

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https://doi.org/10.1038/srep37588

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Journal: Scientific Reports	Publication Date: Nov 21, 2016
Citations: 78	License type: CC BY 4.0

Affiliation: University of Illinois Urbana-Champaign

Abstract

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {AlxGa1−xN}/AlN, (b) Thin-GaN/3 × {AlxGa1−xN}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm2/V∙s) and 2DEG carrier concentration (>1.0 × 1013 cm−2) on Si(111) substrates.

Highlights

AlGaN/GaN high electron mobility transistors (HEMTs) are being investigated for high power high frequency applications as III-nitride (i.e. GaN) materials have high thermal and chemical stability, high breakdown field (>3 MV/cm, 10 times of that of silicon), and high electron saturation velocity (>2.5 × 107 cm/s, 2.5 times of that of silicon
Performance of AlGaN/GaN HEMTs is governed by the two-dimensional electron gas (2DEG) properties, which forms at the AlGaN-GaN hetero-interface and without the need of any doping – thanks to the high conduction band offset and polarization fields between AlGaN and GaN8
To quantify the stress and defectivity, we investigate these stacks using structural, optical and electrical characterization techniques including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high resolution cross-sectional transmission electron microscopy (HR-XTEM), optical microscopy, atomic-force microscopy (AFM), cathodoluminescence (CL), Raman spectroscopy, X-ray diffraction (XRD) {ω/2θ scan, symmetric/asymmetric ωscan, and reciprocal space mapping (RSM)} and Hall effect measurements

Summary

Introduction

AlGaN/GaN high electron mobility transistors (HEMTs) are being investigated for high power high frequency applications as III-nitride (i.e. GaN) materials have high thermal and chemical stability, high breakdown field (>3 MV/cm, 10 times of that of silicon), and high electron saturation velocity (>2.5 × 107 cm/s, 2.5 times of that of silicon). The same AlGaN/GaN HEMT structures need to be grown on Si[111] but with various buffer layers. The same AlGaN/GaN HEMT structures need to be grown on Si[111] but with various buffer layers7 Another important milestone in GaN-on-Si[111] technology is Si[111] wafer-scaling. We grew the same AlGaN/GaN HEMT structures on 200-mm Si[111] substrates using three different buffer layers configurations {such that all wafers are crack-free and have a small bow (

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