Towards a better understanding of trench defects in InGaN/GaN quantum wells

F C-P Massabuau,D Lodié,R A Oliver,L Trinh-Xuan,C J Humphreys,S Rhode,S-L Sahonta,M J Kappers,E J Thrush,F Oehler

doi:10.1088/1742-6596/471/1/012042

F C-P Massabuau, D Lodié + Show 8 more

Open Access

https://doi.org/10.1088/1742-6596/471/1/012042

Copy DOI

Abstract

Trench defects are a commonly occurring feature in InGaN/GaN quantum well (QW) structures. This defect appears at the surface of a structure as a trench enclosing a region of material with peculiar emission properties. Transmission electron microscopy was used to characterise the sub-surface structure of such defect. It consists of a basal-plane stacking fault (BSF) located in the QW stack and bound by a vertical stacking mismatch boundary (SMB) which runs towards the surface and which opens up into pits, which merge to form a trench. Atomic force microscopy and cathodoluminescence were performed on the same individual defects in order to directly correlate the morphology with the emission properties. A strong correlation has been established between the thickness of the trench and the redshift and intensity of the emission of the enclosed region suggesting that bright trench defects emitting at a longer wavelength nucleate early during the growth. Data also suggest that the SMB may act as a non-radiative recombination centre.

Highlights

InGaN/GaN quantum well (QW) structures are a key component of high efficiency opto-electronic devices [1]
It can be seen in figure 2(a) that a basal plane stacking fault (BSF) is located in the QW stack below the defect
The basal-plane stacking fault (BSF) is observed to be bound by a stacking mismatch boundary (SMB) [7] which runs vertically to the apex of the V-shaped ditch (figure 2(d))

Summary

Introduction

InGaN/GaN quantum well (QW) structures are a key component of high efficiency opto-electronic devices [1]. Such structures are characterised by a high density of defects such as threading dislocation [2], V-pits [3] and trench defects (trenches at the surface of the structure enclosing a region of material) [4], which might affect their optical properties. Threading dislocations and Vpits have attracted an intense research effort, trench defects are still poorly understood. This study investigates the structure of trench defects by transmission electron microscopy (TEM) and tries to link the morphology of a defect with its optical properties using a “multi-microscopy analysis” based on atomic force microscopy (AFM) and scanning electron microscopy with cathodoluminescence (SEM-CL)

Methods

Results

Discussion

Conclusion