Deep Ultraviolet Light Emitting Element With AlGaAs Contact Layer
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Solution Overview
Problem
Deep ultraviolet light emitting elements with high Al composition ratio p-type contact layers exhibit initial high light output power but suffer from reliability issues due to abnormalities at the contact interface, leading to reduced performance over time.
Innovation Solution
A deep ultraviolet light emitting element design featuring a p-type contact layer made of non-nitride p-type group III-V semiconductor material or p-type group IV semiconductor material, with a reflectance of 10% or higher at 280 nm, replacing the conventional GaN contact layer to enhance light reflection and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the Al composition ratio of the p-type contact layer is increased to improve light transmittance, then light extraction efficiency is improved, but contact interface abnormalities occur leading to reduced reliability
Solution Approach 1:
The invention changes the material composition parameter by replacing the conventional p-type GaN contact layer with a p-type AlGaAs contact layer having different bandgap and optical properties. This parameter change enables high light transmittance in the deep ultraviolet range while maintaining stable contact interface characteristics, thereby resolving the contradiction between light extraction efficiency and reliability.
Solution Approach 2:
The invention uses a composite structure consisting of a p-type AlGaAs contact layer with specific aluminum composition ratio (0.3 < x ≤ 0.7) combined with a p-type AlGaN semiconductor layer. This composite material approach allows optimization of both optical transmission properties and electrical contact properties, achieving high light extraction efficiency while maintaining contact interface stability.
2Power
If the Al composition ratio of the p-type contact layer is increased to achieve higher initial light output power, then light output power is improved, but the element fails or performance degrades after several minutes of operation
Solution Approach 1:
The invention optimizes the aluminum composition ratio parameter x in the p-type AlGaAs contact layer to the specific range of 0.3 < x ≤ 0.7. This parameter optimization achieves the right balance between light transmittance (affecting light output power) and contact interface stability (affecting operational reliability), allowing sustained high power output without degradation.
3Reliability
If a p-type GaN contact layer is used to establish ohmic contact, then hole density is easily increased, but light transmittance is reduced due to absorption
Solution Approach 1:
The invention extracts the contact function from the conventional p-type GaN material and transfers it to a p-type AlGaAs material. This extraction allows the contact layer to perform its primary function of establishing ohmic contact while removing the harmful light absorption property, as AlGaAs has lower absorption coefficient in the deep ultraviolet range compared to GaN.
Solution Approach 2:
The p-type AlGaAs contact layer acts as an intermediary between the p-type AlGaN semiconductor layer and the metal electrode. It provides good ohmic contact properties while simultaneously serving as an optical window with high transmittance, mediating between electrical and optical requirements.
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 solution provides a deep ultraviolet light emitting element with sustained high light output power and improved reliability by effectively reflecting deep ultraviolet light and reducing contact resistance, outperforming conventional GaN contact layer-based elements.
Implementation Method 1
the p-type contact layer being configured to function as a reflective layer to reflect the deep ultraviolet light, a reflectance of light at a wavelength of 280 nm incident on the p-type contact layer from the p-type first layer being 10% or higher
Data Source
AI summary
Provided are a deep ultraviolet light emitting element that exhibits both high light output power and an excellent reliability, and a method of manufacturing the same. A deep ultraviolet light emitting element 100 of this disclosure comprises an n-type semiconductor layer 30, a light-emitting layer 40, and a p-type semiconductor layers 60, on a substrate 10, in this order. The light-emitting layer 40 emits deep ultraviolet light. The p-type semiconductor layers 60 comprise a p-type first layer 60A and a p-type contact layer 60B directly on the p-type first layer 60A. The p-type contact layer 60B is made of a non-nitride p-type group III-V or p-type group IV semiconductor material, and functions as a reflective layer to reflect the deep ultraviolet light. The reflectance of light at a wavelength of 280 nm incident on the p-type contact layer 60B from the p-type first layer 60A is 10% or higher.