LED with Lateral Transparent Conductive Oxide and Dielectric Mirror
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light emitting diodes (LEDs) with dielectric reflective layers face challenges in connecting the p-layer to the conductive substrate, which requires high temperature processing and introduces light-absorbing via holes that reduce external quantum efficiency.
Innovation Solution
A light emitting diode design that uses a transparent conductive oxide layer to create an electric connection between the p-contact and the p-layer, eliminating the need for via holes by employing a dielectric mirror formed from alternating layers of SiO2 and TiO2, and optionally incorporating a reflective metal layer to enhance light output efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If via holes are created in dielectric reflective layers to connect p-layer to conductive substrate, then electrical connection is achieved, but light absorption increases and external quantum efficiency decreases
Solution Approach 1:
The patent transitions from vertical via-hole connections to lateral edge connections. The n-type contact layer extends laterally to the edge of the dielectric reflective layer, and the p-type contact layer extends laterally to the edge, creating a current path along the edge rather than through the center. This dimensional change eliminates the need for penetrating via holes while maintaining electrical connectivity.
Solution Approach 2:
The invention extracts the light-absorbing metal via holes from the dielectric reflective layer structure. By forming contacts at the edges and extending them laterally, the patent removes the harmful via holes that would penetrate the dielectric layers and absorb light, thereby preserving the optical performance of the reflective layers.
2Reliability
If high temperature processing is used to form metal connections in via holes, then electrical connection is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the processing temperature parameter by eliminating high-temperature metal deposition and via formation steps. Instead, the invention uses lateral extension of doped semiconductor layers that can be formed at lower temperatures, thereby simplifying the manufacturing process and reducing thermal stress on the structure.
3Illumination intensity
If metallic reflective layers are used to redirect photons, then light reflection is achieved, but optical loss increases compared to dielectric mirrors
Solution Approach 1:
The patent employs a composite structure combining dielectric reflective layers with laterally extended semiconductor contact layers. The dielectric layers (such as TiO2 and SiO2) provide high reflectivity with low optical loss, while the laterally extending n-type and p-type contact layers provide electrical connectivity at the edges without interfering with the optical performance of the dielectric mirror.
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 design simplifies the fabrication process, reduces costs, and enhances external quantum efficiency by minimizing photon absorption, thereby improving light output efficiency and reducing the need for high temperature processing.
Implementation Method 1
An ODR has superior reflectance when compared to a DBR, because the ODR reflects light at any incidence angle and polarization
Implementation Method 2
DBRs have low optical loss and high reflectance, but have the disadvantage of effectively reflecting only that light which impinges near the direction normal to the DBR
Implementation Method 3
A light emitting diode design that uses a transparent conductive oxide layer to create an electric connection between the p-contact and the p-layer
Implementation Method 4
ODRs have low optical loss and high reflectance
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A light emitting diode is disclosed that includes an active structure, a first ohmic contact on the active structure, and a transparent conductive oxide layer on the active structure opposite the first ohmic contact. The transparent conductive oxide layer has a larger footprint than said active structure. A dielectric mirror is positioned on the transparent conductive oxide layer opposite said active structure and a second contact is positioned on the transparent conductive oxide layer opposite the dielectric mirror and separated from the active structure.