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Characterisation of InGaN by Photoconductive Atomic Force Microscopy
Thomas F K Weatherley1, Fabien C-P Massabuau2, Menno J Kappers3
1Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK. thomas.weatherley@epfl.ch.
Materials (Basel, Switzerland)
|September 26, 2018
Summary
Photoconductive atomic force microscopy reveals nanoscale variations in Indium Gallium Nitride (InGaN) films. Lower photocurrent on defect ridges is linked to higher turn-on voltage, suggesting potential for improved optoelectronic devices.
Area of Science:
- Semiconductor Physics
- Materials Science
- Nanotechnology
Background:
- Indium Gallium Nitride (InGaN) is crucial for energy-efficient optoelectronics like LEDs.
- Nanoscale structure significantly influences InGaN's optoelectronic properties.
- Understanding these nanoscale effects is key to optimizing device performance.
Purpose of the Study:
- To investigate the impact of nanoscale structure on InGaN optoelectronic properties.
- To characterize InGaN films using Photoconductive Atomic Force Microscopy (PC-AFM).
- To explore the relationship between defect-related nanoscale features and electrical characteristics.
Main Methods:
- Characterization of four InGaN films (In content 5-15%) using PC-AFM.
- Analysis of current-voltage (I-V) curves obtained via PC-AFM.
- Cross-sectional Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDX) for defect analysis.
Main Results:
- Lower photocurrent observed on ridges around defects in InGaN films with In content ≤ 12%.
- PC-AFM I-V analysis indicated higher turn-on voltage on these ridges.
- TEM-EDX revealed an indium-deficient subsurface region around V-pits in lower indium content films.
Conclusions:
- PC-AFM is a valuable technique for probing nanoscale optoelectronic properties in III-nitride semiconductors.
- Observed variations in photocurrent and turn-on voltage are linked to nanoscale structural differences around defects.
- Further investigation is needed to fully elucidate the correlation between subsurface composition and electrical behavior.
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