Vertical LED Trenches Beneath Top Contact
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Solution Overview
Problem
Vertical thin film light emitting devices face challenges in optical extraction due to light being generated beneath top contacts, which are often absorbed, reducing efficiency and potentially causing structural integrity issues with deep trenches.
Innovation Solution
The implementation of a semiconductor structure with trenches beneath the top contact that include a reflective material, directing light away from the top contact without penetrating the active layer, and using a dielectric layer for total internal reflection, along with a distribution of p-contact areas to minimize absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If deep trenches are formed to improve light extraction, then optical efficiency is improved, but structural integrity deteriorates
Solution Approach 1:
The patent changes the depth parameter of trenches from penetrating through the active region to being confined to the cladding layer only. This parameter modification maintains the light extraction function while eliminating the structural integrity problems associated with deep trenches.
Solution Approach 2:
The patent applies different trench depths to different regions: shallow trenches in the cladding layer for light extraction, and no trenches penetrating the active region. This localized quality differentiation optimizes both optical performance and structural strength.
2Productivity
If trenches penetrate the active region to improve light extraction, then optical efficiency is improved, but device reliability deteriorates
Solution Approach 1:
The patent changes the depth parameter of trenches from penetrating through the active region to being confined to the cladding layer only. This parameter modification maintains the light extraction function while eliminating the device reliability problems associated with trenches in the active region.
3Power
If top contact area is increased to reduce resistance, then electrical performance is improved, but light absorption increases
Solution Approach 1:
The patent converts the harmful effect of light absorption by the top contact into a beneficial effect by using the same top contact structure as a mirror. The reflective properties of the top contact are utilized to redirect light away from the active region, transforming the absorption problem into a light management solution.
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 configuration enhances light extraction by preventing absorption under top contacts, improves structural integrity by reducing thermal insulation and cracking risks, and maintains device reliability by using shallower trenches that do not penetrate the active region.
Implementation Method 1
The minimum necessary thickness for this effect is a fraction of an optical wavelength, and depends on the refractive index of the dielectric. For instance with a SiO2 dielectric layer 58, a thickness of at least 50 nm would be suitable
Implementation Method 2
Mirror 45 includes a reflective conductive layer 62 (often a reflective metal layer such as silver or aluminum) and a dielectric layer 58. The dielectric layer is positioned between the semiconductor structure and the reflective conductive layer 62 and also provides electrical isolation in some embodiments.
Data Source
Figure 1~2
Figure 3~4
AI summary
Embodiments of the invention are directed to structures in a vertical light emitting device that prevent light from being generated beneath absorbing structures, and/or direct light away from absorbing structures. Embodiments of the invention include a semiconductor structure including a light emitting layer disposed between an n-type region and a p-type region. A bottom contact is disposed on a bottom surface of the semiconductor structure. The bottom contact is electrically connected to one of the n-type region and the p-type region. A top contact is disposed on a top surface of the semiconductor structure. The top contact is electrically connected to the other of the n-type region and the p-type region. The top contact includes a first side and a second side opposite the first side. A first trench is formed in the semiconductor structure beneath the first side of the top contact. A second trench is formed in the semiconductor structure beneath the second side of the top contact.