Local nanotip arrays sculptured by atomic force microscopy to enhance the light-output efficiency of GaN-based light-emitting diode structures

Nanoscale structure has a large effect on the optoelectronic properties of InGaN, a material vital for energy saving technologies such as light emitting diodes. Photoconductive atomic force microscopy (PC-AFM) provides a new way to investigate this effect. In this study, PC-AFM was used to characterise four thick (∼130 nm) In x Ga 1 − x N films with x = 5%, 9%, 12%, and 15%. Lower photocurrent was observed on elevated ridges around defects (such as V-pits) in the films with x ≤ 12 %. Current-voltage curve analysis using the PC-AFM setup showed that this was due to a higher turn-on voltage on these ridges compared to surrounding material. To further understand this phenomenon, V-pit cross sections from the 9% and 15% films were characterised using transmission electron microscopy in combination with energy dispersive X-ray spectroscopy. This identified a subsurface indium-deficient region surrounding the V-pit in the lower indium content film, which was not present in the 15% sample. Although this cannot directly explain the impact of ridges on turn-on voltage, it is likely to be related. Overall, the data presented here demonstrate the potential of PC-AFM in the field of III-nitride semiconductors.

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REAL-TIME VISUALIZATION OF MORPHOLOGICAL EVOLUTION OF N, N'-di(naphthalene-1-yl)-N, N'-diphthalbenzidine THIN FILMS: VARIABLE TEMPERATURE ATOMIC FORCE MICROSCOPY STUDY

International Journal of Nanoscience ◽

10.1142/s0219581x02000966 ◽

2002 ◽

Vol 01 (05n06) ◽

pp. 725-730 ◽

Cited By ~ 1

Author(s):

M. S. XU ◽

J. B. XU ◽

J. AN

Keyword(s):

Thin Film ◽

Atomic Force Microscopy ◽

Morphological Evolution ◽

Variable Temperature ◽

Glassy State ◽

Microscopy Study ◽

Light Emitting ◽

Force Microscopy ◽

Atomic Force ◽

Real Time Visualization

Variable temperature tapping mode atomic force microscopy is exploited to in situ visualize the morphological evolution of N, N'-di(naphthalene-1-yl)-N, N'-diphthalbenzidine (NPB) thin film. The apparent glass transition of the NPB thin film initially occurred at 60°C, proceeded until 95°C, and crystallization from the glassy state quickly appeared at 135°C. The NPB thin film gradually melted and disappeared when the temperature was above 175°C, revealing the underlying layer. These observations are technically helpful and significant to gauge the temperature dependent lifetime and luminance of organic light-emitting diodes.

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Nanoscale surface electrical properties of indium–tin–oxide films for organic light emitting diodes investigated by conducting atomic force microscopy

Journal of Applied Physics ◽

10.1063/1.1353558 ◽

2001 ◽

Vol 89 (7) ◽

pp. 3976-3979 ◽

Cited By ~ 36

Author(s):

Heh-Nan Lin ◽

Sy-Hann Chen ◽

Gung-Yeong Perng ◽

Show-An Chen

Keyword(s):

Atomic Force Microscopy ◽

Electrical Properties ◽

Tin Oxide ◽

Indium Tin Oxide ◽

Organic Light Emitting Diodes ◽

Light Emitting ◽

Force Microscopy ◽

Atomic Force ◽

Organic Light ◽

Tin Oxide Films

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Colloidal quantum dot active layer electroluminescence in a solid GaN matrix

MRS Proceedings ◽

10.1557/proc-0891-ee03-06 ◽

2005 ◽

Vol 891 ◽

Author(s):

Jennifer Pagan ◽

Edward Stokes ◽

Kinnari Patel ◽

Casey Burkhart ◽

Mike Ahrens

Keyword(s):

Active Layer ◽

Light Emitting Diode ◽

Cdse Quantum Dots ◽

Light Emitting ◽

Force Microscopy ◽

Turn On ◽

Atomic Force ◽

Transmission Line Method ◽

Gan Led ◽

Colloidal Quantum Dot

ABSTRACTIn this paper the preliminary results of incorporating a novel active layer into a GaN light emitting diode (LED) are discussed. Integration of colloidal CdSe quantum dots into a GaN LED active layer is demonstrated. The conductivity of the overgrowth was examined by circular transmission line method (CTLM). Effects on surface roughness due to the active layer incorporation are examined using atomic force microscopy (AFM). LED test devices were fabricated and electroluminescence was demonstrated, the devices exhibit higher turn-on voltages than would be expected for a CdSe active layer.

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High Power 330 nm AlInGaN UV LEDs in the High Injection Regime

MRS Proceedings ◽

10.1557/proc-798-y1.8 ◽

2003 ◽

Vol 798 ◽

Cited By ~ 1

Author(s):

M. Gherasimova ◽

J. Su ◽

G. Cui ◽

J. Han ◽

H. Peng ◽

...

Keyword(s):

Light Emitting Diode ◽

Threading Dislocation ◽

Light Emitting ◽

Force Microscopy ◽

Sapphire Substrates ◽

Atomic Force ◽

Transmission Electron ◽

Dislocation Densities ◽

Dimensional Growth ◽

Uv Leds

ABSTRACTWe report on the growth and testing of the light emitting diode structures incorporating quaternary AlInGaN active region with an emission wavelength of 330 nm. Small area circular devices were fabricated, yielding the output power of 110 μW measured with a bare-chip configuration in a high current injection regime (8 kA/cm2 for a 20 μm diameter device). Structural properties of the constituent epitaxial layers were evaluated by atomic force microscopy and transmission electron microscopy, resulting in the observation of two-dimensional growth morphologies of AlN and AlGaN, and the estimate of threading dislocation densities in the low 109 cm-2 range in the structures grown on sapphire substrates.

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