Radiation-Emitting Semiconductor Chip with Structured Refractive Index Gradient
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Solution Overview
Problem
Radiation-emitting semiconductor chips face reduced light yield due to total reflections at the interface between high refractive index semiconductor materials and surrounding media, leading to inefficient radiation coupling out.
Innovation Solution
The semiconductor chip features a structured area with irregularly arranged structural elements of a first material surrounded by a second material, creating a gradual refractive index transition to reduce reflections and enhance light yield, achieved through the use of an intermediate layer with a mixed refractive index between the two materials, and a passivation or absorber layer to improve beam quality and mode damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high refractive index semiconductor material is used, then radiation generation efficiency is improved, but total reflections at the interface with surrounding media increase, reducing light yield
Solution Approach 1:
The patent introduces an intermediate layer with a refractive index that gradually transitions between the high refractive index semiconductor material and the low refractive index surrounding medium. This intermediate layer acts as a mediator that reduces the abrupt refractive index jump, thereby minimizing total internal reflections and improving light extraction efficiency while maintaining the benefits of high refractive index material for radiation generation.
Solution Approach 2:
The patent modifies the refractive index parameter by creating a gradient structure where the refractive index changes gradually from the semiconductor material through the intermediate layer to the surrounding medium. This parameter change approach transforms the abrupt interface into a gradual transition zone, reducing reflection losses and improving overall light yield.
2Device complexity
If the refractive index transition is abrupt, then device structure is simple, but radiation coupling out efficiency is reduced due to total reflections
Solution Approach 1:
The intermediate layer serves as a mediator structure that bridges the high refractive index semiconductor and the low refractive index surrounding medium. While this adds a layer to the device structure, it significantly improves radiation coupling out efficiency by reducing total internal reflections at the interface.
Solution Approach 2:
The patent employs a composite structure consisting of the semiconductor material and the intermediate layer with different refractive indices. This composite material approach allows for optimized radiation coupling by combining materials with different optical properties to create a gradient refractive index profile.
3Reliability
If structural elements with small width and distance are used, then refractive index transition is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the geometric parameters of the intermediate layer, including the width and spacing of structural elements, to achieve an effective refractive index that provides the desired gradient transition. By carefully selecting these parameters, the patent balances the quality of refractive index transition with manufacturability, avoiding excessively small dimensions that would require ultra-precise manufacturing.
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 approach increases radiation power output while maintaining low threshold currents and reducing transverse mode hops, improving beam quality and light coupling efficiency by minimizing refractive index jumps and promoting deeper penetration of optical waves into the semiconductor layers.
Implementation Method 1
adjusting a refractive index transition that occurs between a first medium with a first refractive index and a second medium with a second refractive index in a desired manner by means of the shape, size and/or density of structural elements
Implementation Method 2
total reflections can easily occur when radiation is coupled out at an interface between the semiconductor chip and the surrounding medium, which leads to a reduced light yield
Data Source
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AI summary
The invention relates to a radiation-emitting semiconductor chip (1) comprising an active zone (2) for generating radiation of wavelength lambda and a structured region (3) with irregularly arranged structural elements. These elements comprise a first material with a first refractive index n1 and are surrounded by a medium comprising a second material with a second refractive index n2. The thickness of an intermediate layer comprising the structural elements and the medium corresponds to a maximum height of the structural elements, wherein for an effective refractive index neff of the intermediate layer n2 < neff < n1, and wherein the base area g of the respective structural elements is less than the height h of the respective structural elements. Furthermore, a method for manufacturing such a semiconductor chip is described.