Analysis of reaction between c+a and -c+a dislocations in GaN layer grown on 4-inch Si(111) substrate with AlGaN/AlN strained layer superlattice by transmission electron microscopy

Yoshihiro Sugawara,Takashi Egawa,Arata Watanabe,Makoto Miyoshi,Yukari Ishikawa

doi:10.1063/1.4948451

Abstract

The behavior of dislocations in a GaN layer grown on a 4-inch Si(111) substrate with an AlGaN/AlN strained layer superlattice using horizontal metal-organic chemical vapor deposition was observed by transmission electron microscopy. Cross-sectional observation indicated that a drastic decrease in the dislocation density occurred in the GaN layer. The reaction of a dislocation (b=1/3[-211-3]) and anothor dislocation (b =1/3[-2113]) to form one dislocation (b =2/3[-2110]) in the GaN layer was clarified by plan-view observation using weak-beam dark-field and large-angle convergent-beam diffraction methods.

Highlights

The behavior of dislocations in a GaN layer grown on a 4-inch Si(111) substrate with an AlGaN/AlN strained layer superlattice using horizontal metal-organic chemical vapor deposition was observed by transmission electron microscopy
High-angle annular dark-field (HAADF) observation was performed with a scanning transmission electron microscope (STEM) (JEOL JEM-2100F)
In the cross-sectional images, the dislocation density was too high to find a dislocation that was not affected by the strain fields of other dislocations, i.e., suitable for large-angle convergent-beam electron diffraction (LACBED) observation

Summary

Introduction

Power devices fabricated from AlGaN/GaN high-electron-mobility transistors (HEMTs) are expected to realize high performance due to their highbreak down voltage, low on-resistance, and high electron mobility.[1,2,3] GaN growth on a Si substrate is one of the most useful methods for providing large-area GaN wafers at a low cost.[4,5,6,7,8] As aresult of several breakthroughs,[9,10] an AlGaN/GaN HEMT on Si demonstrated a breakdown voltage of over 1400 V.10 the large lattice and thermal expansion mismatches between Si and GaN produce high-density dislocations in a GaN layer.[11,12,13] Decreasing the dislocation density in a GaN layer has been a major issue because the dislocations are considered to deteriorate the reliability and life of devices. Power devices fabricated from AlGaN/GaN high-electron-mobility transistors (HEMTs) are expected to realize high performance due to their highbreak down voltage, low on-resistance, and high electron mobility.[1,2,3] GaN growth on a Si substrate is one of the most useful methods for providing large-area GaN wafers at a low cost.[4,5,6,7,8] As aresult of several breakthroughs,[9,10] an AlGaN/GaN HEMT on Si demonstrated a breakdown voltage of over 1400 V.10. The large lattice and thermal expansion mismatches between Si and GaN produce high-density dislocations in a GaN layer.[11,12,13] Decreasing the dislocation density in a GaN layer has been a major issue because the dislocations are considered to deteriorate the reliability and life of devices. Investigating the mechanism by which the dislocation density is decreased in a heteroepitaxial GaN layer will open the way to developing a GaN layer with low dislocation density

Methods

Results

Conclusion