Light-Emitting Device with Non-Polar Growth Plane and Roughened Surface
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Solution Overview
Problem
Nitride-based light emitting devices with c-plane growth substrates suffer from efficiency droop due to spontaneous and piezoelectric polarization, and sapphire substrates have low thermal conductivity, leading to reduced heat dissipation and lifespan, especially at high current operations.
Innovation Solution
A light emitting device with a non-polar or semi-polar growth plane, featuring a light emitting structure with a conductive oxide layer and a reflective electrode layer, and a roughened surface with protrusions to enhance light extraction efficiency, which minimizes polarization effects and improves heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a c-plane growth substrate is used, then the light emitting device can be fabricated with conventional processes, but spontaneous and piezoelectric polarization occur causing efficiency droop
Solution Approach 1:
The patent changes the crystal orientation parameter from c-plane to non-polar or semi-polar planes (a-plane, m-plane, or semi-polar planes), which fundamentally alters the polarization characteristics of the nitride semiconductor layer, thereby eliminating spontaneous and piezoelectric polarization effects that cause efficiency droop
2Ease of manufacture
If a sapphire substrate is used as growth substrate, then the light emitting device can be fabricated, but thermal conductivity is low reducing heat dissipation efficiency
Solution Approach 1:
The patent employs a composite substrate structure combining sapphire substrate with aluminum nitride (AlN) buffer layer and potentially other thermal management layers, where the AlN layer provides superior thermal conductivity to enhance heat dissipation while maintaining the benefits of sapphire substrate for epitaxial growth
3Reliability
If a non-polar or semi-polar homogeneous growth substrate is used, then efficiency deterioration due to polarization is minimized, but light extraction efficiency is reduced due to different growth and optical characteristics
Solution Approach 1:
The patent applies localized surface roughening treatment to specific regions of the light emitting structure, creating protrusions with controlled dimensions and distributions that enhance light extraction locally without affecting the overall non-polar or semi-polar crystal structure and its favorable polarization characteristics
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 improves light extraction efficiency and heat dissipation, leading to enhanced luminous efficacy and reliability, even at high current operations, by addressing the limitations of c-plane growth substrates.
Implementation Method 1
a conductive oxide layer in ohmic contact with the second conductivity type semiconductor layer
Implementation Method 2
a reflective electrode layer disposed on the conductive oxide layer
Implementation Method 3
the light emitting structure has a non-polar or semi-polar growth plane, an upper surface of the second conductivity type semiconductor layer includes a non-polar or semi-polar plane
Data Source
AI summary
Disclosed is a light-emitting device. The light-emitting device comprises: a light-emitting structure comprising a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; a first contact electrode which ohmically contacts the first conductive semiconductor layer; a second contact electrode which is disposed on the second conductive semiconductor layer; and an insulation layer which is disposed on the light-emitting structure and insulates the first contact electrode and the second contact electrode, wherein the light-emitting structure has a non-polar or semi-polar growth surface; the upper surface of the second conductive semiconductor layer comprises a non-polar or semi-polar surface; and the second contact electrode comprises a conductive oxide layer which ohmically contacts the second conductive semiconductor layer, and a reflective electrode layer disposed on the conductive oxide layer.