Nitride Semiconductor VCSEL with Conductive Bragg Reflectors
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Solution Overview
Problem
Existing nitride semiconductor vertical cavity surface emitting lasers face challenges in achieving efficient current injection and heat dissipation due to the use of insulating or dielectric Bragg reflectors with low electrical conductivity, leading to high threshold currents and reduced emission efficiency.
Innovation Solution
A method of manufacturing nitride semiconductor light emitting elements involves forming a stacked layer body with conductive-type layers and a light emitting layer, followed by the creation of dielectric Bragg reflectors and electrodes to ensure uniform current distribution and improved heat dissipation, using a supporting substrate and a connecting electrode to facilitate efficient electric current injection and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a Bragg reflector is made of a nitride semiconductor with extremely low electrical conductivity or a dielectric material, then the reflectance is improved, but the electrical conductivity deteriorates
Solution Approach 1:
The device is divided into distinct functional regions: the Bragg reflector is segmented from the light emitting layer and contact structure. This allows the Bragg reflector to be optimized for optical reflection while the contact structure handles electrical conduction independently.
Solution Approach 2:
A transparent electrode is introduced as an intermediary between the dielectric Bragg reflector and the light emitting layer. This transparent electrode provides the necessary electrical conductivity pathway while allowing optical signals to pass through to reach the light emitting layer.
2Reliability
If two electric contact portions are formed on an upper surface of the p-type layer and the n-type layer, then the electrical connection is improved, but the current distribution uniformity deteriorates
Solution Approach 1:
The contact structure is extended into the vertical dimension by forming a protrusion that penetrates through the light emitting layer. This allows the contact portions to be positioned at different heights, enabling uniform current distribution across the element region while maintaining reliable electrical connection.
Solution Approach 2:
The contact structure exhibits local quality variations: the protrusion region provides enhanced current distribution control within the element region, while the broader contact portions ensure reliable electrical connection. Each region is optimized for its specific function.
3Reliability
If the current density becomes locally high, then the electrical connection is improved, but the heat generation increases
Solution Approach 1:
By extending the contact structure vertically with a protrusion, the current is distributed more uniformly across the element region rather than concentrating at a single plane. This dimensional extension reduces local heat generation while maintaining effective electrical connection.
Solution Approach 2:
The protrusion structure, which could be seen as adding complexity, actually converts the potential harm of localized high current density into a benefit by spreading the current distribution. The extended contact path allows heat to dissipate more effectively while maintaining electrical connection reliability.
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 enables the production of high-efficiency nitride semiconductor light emitting elements with improved current distribution and reduced heat generation, enhancing the matching of lateral light and gain profiles and achieving efficient emission and oscillation.
Implementation Method 1
forming a first Bragg reflector made of a dielectric multilayer film above the first conductive-type layer; forming over the exposed second conductive-type layer a second Bragg reflector made of a dielectric multilayer film so that the second Bragg reflector faces the first Bragg reflector
Implementation Method 2
a light emitting layer 53, and a p-type nitride semiconductor layer 54 are stacked on a sapphire substrate 50 in this order... uniformly distribute the current supplied to the element region... to obtain a light emitting element having high efficiency
Data Source
AI summary
A method of manufacturing a nitride semiconductor light emitting element includes: forming a stacked layer body of a nitride semiconductor having a second conductive-type layer, a light emitting layer, and a first conductive-type layer stacked on a growth substrate in this order; forming a first Bragg reflector made of a dielectric multilayer film above the first conductive-type layer; forming a first electrode over the first Bragg reflector with the first electrode being electrically connected to the first conductive-type layer; bonding the stacked layer body to a supporting substrate via the first Bragg reflector and the first electrode; removing the growth substrate from the stacked layer body to expose the second conductive-type layer; and forming over the exposed second conductive-type layer a second electrode and a second Bragg reflector made of a dielectric multilayer film so that the second Bragg reflector faces the first Bragg reflector across the stacked layer body.