Semiconductor Light Emitting Device Inclined Substrate
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Solution Overview
Problem
Conventional semiconductor light emitting devices suffer from luminance degradation due to light absorption caused by multiple reflections of light beams at critical angles, leading to reduced external quantum efficiency and increased heat saturation issues.
Innovation Solution
A semiconductor light emitting device configuration featuring a transparent substrate with a parallel surface and an inclined surface, where the inclined surface is designed to redirect light beams incident at critical angles, reducing multiple reflections and enhancing light emission efficiency, along with a current narrowing portion and specific electrode configurations to optimize light output and heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a GaP current diffusion layer with thickness of 50 to 100 μm is used to ensure mechanical strength, then the wafer can be handled during manufacturing, but the growth time is prolonged and the cost increases
Solution Approach 1:
The current diffusion layer is divided into two distinct layers: a GaP layer (5-20 μm thick) for mechanical strength and a AlGaInP-based current diffusion layer (5-20 μm thick) for electrical function. This segmentation allows each layer to be optimized independently, reducing the total thickness from 50-100 μm to 10-40 μm while maintaining both mechanical strength and electrical performance.
Solution Approach 2:
Different regions of the device are assigned different material properties: the GaP layer provides mechanical strength where needed, while the AlGaInP-based layer provides current diffusion functionality. This local quality assignment allows the structure to meet multiple requirements simultaneously with reduced overall thickness.
2Loss of time
If the layer thickness of the GaP current diffusion layer is reduced to 40 μm or less, then the growth time is shortened and cost is reduced, but the wafer becomes extremely fragile and breaks during handling
Solution Approach 1:
The current diffusion function is segmented between two layers: a thin GaP layer (5-20 μm) that provides sufficient mechanical strength without excessive thickness, and a thin AlGaInP-based layer (5-20 μm) that provides the current diffusion function. This allows both reduced growth time and maintained mechanical strength.
Solution Approach 2:
The device uses a composite structure combining GaP and AlGaInP materials in a layered configuration. The GaP layer contributes mechanical strength, while the AlGaInP layer contributes current diffusion properties, creating a composite structure that achieves both reduced thickness and maintained functionality.
3Device complexity
If a conventional flat substrate structure is used, then the device structure is simple, but light beams undergo multiple reflections at critical angles causing luminance degradation
Solution Approach 1:
The substrate is designed with an asymmetric structure featuring an inclined surface (first surface) at a specific angle (e.g., 45 degrees) relative to the light emission direction, while the opposite surface remains flat (second surface). This asymmetric geometry prevents symmetric multiple reflections of light beams, reducing luminance degradation while maintaining relatively simple manufacturing processes.
Solution Approach 2:
The flat two-dimensional substrate structure is modified by adding a dimensional element through the inclined surface. This creates a three-dimensional geometry that alters light propagation paths, preventing multiple reflections that occur in flat structures while adding minimal complexity to the overall device.
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 solution significantly increases the external quantum efficiency and luminance of the semiconductor light emitting device by minimizing light absorption and improving heat radiation, allowing for higher current densities without heat saturation, thereby enhancing overall performance.
Implementation Method 1
light beams incident to a reflection surface in the semiconductor light emitting device at angles not less than a critical angle are totally reflected
Implementation Method 2
the inclined surface adjoining the parallel surface and inclined to the parallel surface... light beams coming incident to the inclined surface come out of the semiconductor light emitting device
Data Source
AI summary
A semiconductor light emitting device includes a first conductivity-type first semiconductor layer; an emission layer; a second conductivity-type second semiconductor layer; and a second conductivity-type transparent substrate transparent to light beams from the emission layer and directly bonded to the second semiconductor layer. The transparent substrate has a parallel surface almost parallel to the emission layer on an opposite side of the emission layer, and an inclined surface adjoining the parallel surface and inclined to the parallel surface. Light beams totally reflected on the parallel surface and light beams totally reflected on a side surface of the transparent substrate come incident to the inclined surface at an angle smaller than the critical angle, and emit out of the semiconductor light emitting device.