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Analysis for light emitting diode (LED) by atom probe tomography

The light emission performance of LED with InGaN multiple quantum well (MQW) depends on the condition of crystal growth. Structural analysis of each layer and quantitative analysis for dopant distribution are carried out using TEM and APT.

Quantitative evaluation of MQW layers using TEM and APT

A general view is that an uneven Indium (In) composition causes carrier diffusion in gallium-nitride devices with an InGaN MQW layer, significantly affecting their light-emitting characteristics. TNA offers quantitative evaluation of the MQW layer, including film thickness, In composition, in-plane distribution and variation.

Cross-sectional TEM image of an MQW layer
Cross-sectional TEM image of MQW

3D atom probe image of an MQW layer
APT image of MQW

Observation of MQW layers by TEM and APT

In atom distribution in an InGaN layer

Distribution of Indium atom in InGaN

Visualization of an InGaN layer on the isoconcentration surface

Visualization of iso-concentration surface of InGaN

Variations in concentration can be quantified based on the roughness Sa (Ra) value on the isoconcentration surface.
The dispersion can be calculated from
the raughness of iso-concentration surface.

Distribution of magnesium in p-GaN layer

LED has pn diode structure in which active layer of MQW is sandwiched by p and n type semiconductor. Holes are provided through p-type, and electrons are provided through n-type.

Mg is doped as an acceptor in general LED with InGaN MQW structure. It is found that Mg is clustering and distributing locally by APT (analysis).

Mg atom distribution and Mg atom clusters in the p-type GaN layer
Distribution and clusters of Mg
atoms in p-GaN layer

Variations in Mg concentration on an isoconcentration surface
Dispersion of Mg concentration
in p-GaN layer by iso-concentration

Distribution and concentration dispersion of Mg atoms

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[Last updated: April 18, 2019]

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