Vertical LED Structure for Current Distribution and Heat Dissipation
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Solution Overview
Problem
Light emitting diodes (LEDs) face challenges in achieving high light efficiency due to current concentration at specific regions, high sheet resistance in conductive semiconductor layers, and thermal stress issues during wafer bonding, which affect light emitting area and heat dissipation.
Innovation Solution
The implementation of a light emitting device structure that includes a support substrate, a wafer bonding layer, a current blocking layer, a reflective current spreading layer, a current injection layer, a superlattice structure layer, and specific electrode layers to distribute current evenly and enhance light extraction, while minimizing thermal stress through careful material selection and bonding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a lateral type LED structure is used with growth substrate, then the device can be manufactured, but the light emitting area is reduced and light efficiency is degraded
Solution Approach 1:
The patent inverts the conventional lateral LED structure by forming electrodes vertically on the growth substrate. The first electrode is formed through the growth substrate to contact the first conductive semiconductor layer, and the second electrode contacts the second conductive semiconductor layer, transforming the current flow from lateral to vertical direction and thereby increasing the light emitting area without compromising manufacturability
Solution Approach 2:
The patent transitions from a two-dimensional lateral current flow to a three-dimensional vertical current flow by forming electrodes that extend through the growth substrate. This dimensional change allows current to flow vertically through the light emitting semiconductor layer, significantly increasing the effective light emitting area while maintaining the same footprint on the substrate
2Ease of manufacture
If a lateral type LED structure is used with growth substrate, then the device can be manufactured, but heat dissipation is difficult due to low thermal conductivity
Solution Approach 1:
The patent introduces a heat dissipation layer as an intermediary between the growth substrate and the light emitting semiconductor layer. This heat dissipation layer has high thermal conductivity and serves as a thermal pathway to conduct heat away from the active region, effectively solving the heat dissipation problem while maintaining the lateral structure's manufacturability advantages
3Reliability
If transparent current injection layer including ITO or ZnO is used, then ohmic contact interface can be formed, but schottky contact interface is formed instead through deposition and heat treatment processes
Solution Approach 1:
The patent modifies the deposition parameters and heat treatment conditions to prevent the formation of schottky contacts. By controlling the deposition temperature, thickness, and subsequent annealing parameters, the patent ensures that the transparent current injection layer forms ohmic contacts with the semiconductor layers, maintaining reliable electrical characteristics while being compatible with standard manufacturing processes
4Strength
If wafer bonding process is performed at high temperature, then bonding strength is improved, but cracks or breakages occur due to thermal expansion coefficient difference
Solution Approach 1:
The patent applies different thermal expansion coefficient materials in specific locations to compensate for stress. By selecting materials with matched thermal expansion coefficients for the wafer bonding interface, the patent enables high-temperature bonding without causing cracks or breakages in the light emitting semiconductor layer, thereby achieving both strong bonding and structural integrity
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 structure improves electrical characteristics and light efficiency by preventing current concentration, increasing the light emitting area, and facilitating effective heat dissipation, thereby enhancing the overall performance of the LED.
Implementation Method 1
the active layer generates light according to current applied to the first and second conductive semiconductor layers
Implementation Method 2
heat is transferred through the second electrode layer, so the heat dissipation is easy
Data Source
AI summary
Disclosed are a light emitting device and a method of manufacturing the same. The light emitting device includes a support substrate, a wafer bonding layer over the support substrate, a second electrode layer, which includes a current blocking layer and a reflective current spreading layer, over the wafer bonding layer, a current injection layer over the second electrode layer, a superlattice structure layer over the current injection layer, a second conductive semiconductor layer over the superlattice structure layer, an active layer over the second conductive semiconductor layer, a first conductive semiconductor layer over the active layer, and a first electrode layer over the first conductive semiconductor layer.