Silver-Base Alloy Reflector Layer for LED Ohmic Contact
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Solution Overview
Problem
Conventional light-emitting semiconductor devices face challenges in achieving high efficiency due to light absorption by the substrate and high electrical resistance, which complicates the dual objective of low forward voltage and high reflectivity, and the manufacturing process is hindered by interactions between the reflector and semiconductor regions.
Innovation Solution
A light-emitting semiconductor device with a silver-base alloy reflector layer containing additives like copper, gold, or palladium, which provides improved reflectivity and ohmic contact without oxidation or sulfurization, allowing for a more efficient light redirection and bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a solid metal-made reflector layer is used, then reflectivity is improved, but contact ohmicity deteriorates
Solution Approach 1:
The patent applies composite materials by combining a solid metal-made reflector layer (providing high reflectivity) with an open-worked alloy layer (providing low-resistance contact). This composite structure allows both the reflector layer and the semiconductor region to be in intimate contact, achieving both high reflectivity and low forward voltage requirement simultaneously.
2Reliability
If an open-worked alloy layer is used, then contact ohmicity is improved, but reflectivity deteriorates
Solution Approach 1:
The patent uses a composite structure where the open-worked alloy layer is combined with a solid metal-made reflector layer. The alloy layer provides low-resistance contact while the solid reflector layer provides high reflectivity, overcoming the limitation of the alloy layer alone.
3Productivity
If a reflector layer is placed on the substrate, then light redirection is improved, but light absorption by substrate worsens efficiency
Solution Approach 1:
The patent extracts the reflector layer from the substrate and places it directly on the light-generating semiconductor region. This eliminates the substrate's light absorption problem while maintaining the light redirection function, as the reflector is now in intimate contact with the semiconductor region without the substrate in between.
4Ease of manufacture
If thermal treatments are applied during manufacturing, then bonding is improved, but reflectivity deteriorates due to interaction between reflector and semiconductor regions
Solution Approach 1:
The patent introduces an open-worked alloy layer as an intermediary between the solid metal-made reflector layer and the light-generating semiconductor region. This intermediary layer prevents harmful interactions during thermal treatments while maintaining both bonding quality and reflectivity, as it acts as a protective barrier during the bonding process.
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 silver-base alloy reflector layer achieves high reflectivity and low forward voltage requirements, enhancing the efficiency of light-emitting semiconductor devices by preventing oxidation and sulfurization, thus improving contact ohmicity and manufacturing reliability.
Implementation Method 1
an electroconductive reflector layer interposed between the baseplate and the light-generating semiconductor region
Implementation Method 2
The reflector layer is made from a silver-base alloy containing a major proportion of silver and at least one additive selected from among copper, gold, palladium, neodymium, silicon, iridium, nickel, tungsten, zinc, gallium, titanium, magnesium, yttrium, indium, and tin
Implementation Method 3
which provides improved reflectivity and ohmic contact without oxidation or sulfurization
Data Source
AI summary
An LED has a light-generating semiconductor region formed on a baseplate via an electroconductive reflector layer. The light-generating semiconductor region has an active layer sandwiched between a pair of claddings of opposite conductivity types for generating light. For good ohmic contact with the light-generating semiconductor region without any substantive diminution of reflectivity compared to that of unalloyed silver, the reflector layer is made from a silver-base alloy containing a major proportion of silver and at least either one of copper, gold, palladium, neodymium, silicon, iridium, nickel, tungsten, zinc, gallium, titanium, magnesium, yttrium, indium, and tin.