Doped III-Nitride LED Light Emitting Layer for High Current Efficiency
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Solution Overview
Problem
Commercial III-nitride light-emitting devices with InGaN light emitting layers suffer decreasing efficiency at high current densities due to increasing current density, despite improved performance at low drive currents.
Innovation Solution
A semiconductor light-emitting device with a III-nitride light emitting layer doped between 6x10^18 cm^-3 and 5x10^19 cm^-3, having a thickness of 50 Å to 250 Å and graded InN composition, which includes one or more local maxima in the band gap without quantum confinement, thereby maintaining high efficiency at high current densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the current density is increased to improve light output, then the brightness increases, but the quantum efficiency decreases
Solution Approach 1:
The patent changes the doping concentration parameter in the light emitting layer from conventional levels (1x10^18 to 1x10^19 cm^-3) to a higher range (6x10^18 to 5x10^19 cm^-3). This parameter change modifies the electrical and optical properties of the InGaN layer, enabling it to maintain high quantum efficiency even at high current densities by reducing non-radiative recombination losses.
2Illumination intensity
If the light emitting layer thickness is increased to improve light extraction, then the light output increases, but the internal quantum efficiency decreases
Solution Approach 1:
The patent optimizes the thickness parameter of the light emitting layer to a specific range (50-250 Å) and combines it with elevated doping concentrations. This combined parameter optimization achieves a balance where sufficient thickness allows for improved light extraction while the high doping level maintains high internal quantum efficiency by reducing carrier localization and non-radiative recombination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device exhibits improved external and internal quantum efficiency, with reduced drop in efficiency at high current densities and stable peak wavelength, by optimizing dopant concentration and layer thickness, and incorporating optional spacer and blocking layers for enhanced material quality and light extraction.
Implementation Method 1
Semiconductor light-emitting devices including light emitting diodes (LEDs)... III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers... a light emitting or active region formed over the n-type layer or layers
Implementation Method 2
Such devices are mounted so light is extracted either through the contacts (known as an epitaxy-up device) or through a surface of the device opposite the contacts (known as a flip chip device)
Data Source
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AI summary
A Ill-nitride light emitting layer is disposed between an n-type region and a p- type region. The light emitting layer is a doped thick layer. In some embodiments, the light emitting layer is sandwiched between two doped spacer layers.