LED Active Layer Pits for Hole Injection Efficiency
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Solution Overview
Problem
High power LED light sources require multiple LEDs due to individual LED limitations in power and efficiency, leading to increased cost and heat dissipation issues, with existing technologies struggling to enhance conversion efficiency without compromising light output or increasing costs.
Innovation Solution
A light emitting device with an active layer featuring pits where sub-layer sidewalls are in contact with p-type semiconductor material, allowing for increased hole injection through sidewalls rather than the top sub-layer, thereby reducing hole density and enhancing overall efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the current is increased through the LED device to generate more light, then the light output increases, but the conversion efficiency decreases and heat dissipation problems increase
Solution Approach 1:
The active layer is divided into multiple sub-layers (first sub-layer, second sub-layer, third sub-layer) with different functions. The first sub-layer receives holes from the p-doped layer, the second sub-layer generates light through electron-hole recombination, and the third sub-layer transports holes to the p-doped layer. This segmentation allows optimized hole distribution and reduced non-radiative recombination, maintaining high efficiency at high current densities.
Solution Approach 2:
The second sub-layer acts as an intermediary between the first and third sub-layers, facilitating efficient energy transfer. It receives electrons from the n-doped layer and holes from the first sub-layer, enabling radiative recombination while protecting the hole transport function of the third sub-layer. This intermediary structure optimizes the conversion efficiency throughout the device.
2Power
If multiple LEDs are used to achieve high power levels, then the required light output is met, but the cost and device complexity increase
Solution Approach 1:
The invention changes the structural parameters of the active layer by introducing a multi-sub-layer configuration with specific thickness ratios and material compositions. This allows a single LED to operate at higher power levels (up to several watts) by improving current distribution and reducing efficiency droop, thereby reducing the need for multiple LEDs to achieve the same total power output.
3Productivity
If the current density is increased to improve light generation, then more light is produced per LED, but the fraction of holes recombining without producing light increases
Solution Approach 1:
Different sub-layers are assigned different local qualities and functions: the first sub-layer is optimized for hole reception from the p-doped layer, the second sub-layer for radiative recombination and light generation, and the third sub-layer for efficient hole transport to the p-doped layer. This local optimization ensures that each region performs its specific function efficiently, maintaining high injection efficiency even at high current densities.
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
This approach increases the efficiency of light production per LED, reducing the number of LEDs needed for a given light source, lowering operational costs, and maintaining light output while minimizing heat dissipation challenges.
Implementation Method 1
Light is generated when holes from the p-doped layer combine with electrons from the n-doped layer in the active layer
Data Source
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AI summary
A light emitting device and method for making the same is disclosed. The light-emitting device includes an active layer sandwiched between a p-type semiconductor layer and an n-type semiconductor layer. The active layer emits light when holes from the p-type semiconductor layer combine with electrons from the n-type semiconductor layer therein. The active layer includes a number of sub-layers and has a plurality of pits in which the side surfaces of a plurality of the sub-layers are in contact with the p-type semiconductor material such that holes from the p-type semiconductor material are injected into those sub-layers through the exposed side surfaces without passing through another sub-layer. The pits can be formed by utilizing dislocations in the n-type semiconductor layer and etching the active layer using an etching atmosphere in the same chamber used to deposit the semiconductor layers without removing the partially fabricated device.