Light Emitting Device Recess Current Diffusion Layer
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Solution Overview
Problem
Current light emitting devices face challenges in achieving high brightness due to light absorption in GaAs substrates and difficulties in external light extraction efficiency, particularly with ITO electrodes, which have low light transmittance and poor ohmic contact, and complex manufacturing processes.
Innovation Solution
A light emitting device structure featuring a semiconductor light emitting layer, a current diffusion layer with a recess in a non-forming region of the upper electrode, and a thin-wire electrode surrounding the bonding electrode, which increases lateral current diffusion and reduces optical absorption, combined with a translucent GaP substrate and a reflecting layer to enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a recess is etched more deeply than the light emitting layer to expose the end surface, then external light extraction efficiency is improved, but the manufacturing process becomes more complex and crystal surface degradation occurs
Solution Approach 1:
The device is segmented into distinct functional layers: the light emitting layer remains protected and intact, while the current diffusion layer is separately etched to form the recess. This segmentation allows the light extraction function to be achieved without exposing or damaging the light emitting layer, thereby simplifying the manufacturing process compared to etching through the entire structure.
Solution Approach 2:
The current diffusion layer serves as an intermediary layer between the light emitting layer and the upper electrode. By forming the recess in this intermediate layer rather than in the light emitting layer itself, the patent achieves light extraction enhancement while protecting the crystal surface of the light emitting layer from degradation.
2Illumination intensity
If ITO or other transparent electrode is used on the chip surface to increase light extraction efficiency, then light extraction is improved, but light transmittance is low and ohmic contact is difficult to achieve
Solution Approach 1:
The patent changes the material parameter of the upper electrode from conventional transparent conductive oxides like ITO to a metal layer. This parameter change improves both the electrical conductivity (achieving better ohmic contact) and the light transmittance, thereby resolving the contradiction between light extraction efficiency and contact quality.
3Manufacturing precision
If GaAs substrate is used for the light emitting layer, then lattice matching is achieved, but light absorption occurs and brightness decreases
Solution Approach 1:
The patent extracts the light emitting layer from the GaAs substrate and places it on a GaP substrate. This extraction removes the light-absorbing GaAs substrate from the optical path while maintaining the lattice-matched growth conditions through the bonding layer, thereby eliminating light absorption and increasing brightness.
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 increases light extraction efficiency and maintains high brightness while simplifying the manufacturing process, reducing the risk of crystal defects and improving reliability by avoiding deep etching and maintaining a non-exposed light emitting layer.
Implementation Method 1
a current diffusion layer provided between the light emitting layer and the upper electrode and made of semiconductor
Implementation Method 2
the current diffusion layer including a recess that is formed in a non-forming region of the upper electrode and capable of emitting light emitted from the light emitting layer
Implementation Method 3
a GaP substrate that is lattice mismatched with GaAs but translucent
Implementation Method 4
a reflecting layer provided on the other major surface
Data Source
AI summary
A light emitting device includes a light emitting layer made of semiconductor; an upper electrode including a bonding electrode capable of connecting a wire thereto and a thin-wire electrode surrounding the bonding electrode with a spacing and including a junction with the bonding electrode, and a current diffusion layer provided between the light emitting layer and the upper electrode and made of semiconductor, the current diffusion layer including a recess that is formed in a non-forming region of the upper electrode and capable of emitting light emitted from the light emitting layer.