AlGaN UV Emitter Structure for Stable Crystal Growth Yield
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Solution Overview
Problem
The production of nitride semiconductor ultraviolet light-emitting elements is hindered by fluctuations in characteristics due to drift in crystal growth apparatus, making stable yield difficult to achieve.
Innovation Solution
The nitride semiconductor ultraviolet light-emitting element features a structure with n-type and p-type AlGaN-based semiconductor layers, where the n-type layer includes stratiform regions with a specific AlGaN composition ratio and multi-step terraces, stabilizing the AlN mole fraction through metastable AlGaN formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type contact layer with low AlN mole fraction is formed to improve ohmic contact with the p-electrode, then electrical contact quality is improved, but ultraviolet light extraction efficiency deteriorates due to light absorption in the contact layer
Solution Approach 1:
The patent extracts the light extraction function from the p-type contact layer by removing the contact layer entirely. Instead, a reflective layer is introduced at the bottom of the n-type layer to reflect ultraviolet light upward through the active layer and out through the top surface, eliminating the light absorption problem while maintaining good ohmic contact through the n-type layer
2Productivity
If the AlN mole fraction in the n-type layer is increased to improve carrier localization and luminous efficiency, then device performance is improved, but manufacturing stability deteriorates due to sensitivity to crystal growth apparatus drift
Solution Approach 1:
The patent changes the AlN mole fraction parameter from a high value (60-66%) that provides good carrier localization but poor manufacturing stability, to a lower value (30-40%) that reduces sensitivity to crystal growth apparatus drift while maintaining acceptable device performance through the reflective layer structure
Solution Approach 2:
The patent creates local quality variations by forming stratiform regions with different AlN mole fractions within the n-type layer. These regions include Ga-rich areas with lower AlN content that are less sensitive to manufacturing variations, allowing the device to maintain good performance while improving production stability
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 structure suppresses variations in device characteristics, ensuring stable production and improved luminous efficiency by localizing carriers and maintaining consistent emission properties.
Implementation Method 1
the n-type layer includes stratiform regions with a specific AlGaN composition ratio and multi-step terraces, stabilizing the AlN mole fraction through metastable AlGaN formations
Implementation Method 2
by passing a forward current from the p-type nitride semiconductor layer toward the n-type nitride semiconductor layer, light emission corresponding to the band gap energy due to recombination of carriers (electrons and holes) occurs in the active layer
Data Source
AI summary
A nitride semiconductor ultraviolet light-emitting element is provided. The element includes a light-emitting element structure part with an n-type layer, an active layer, and a p-type layer stacked vertically, which are made of AlGaN-based semiconductors with wurtzite structure. The n-type layer has an n-type AlGaN-based semiconductor, the active layer has well layers including an AlGaN based semiconductor, and the p-type layer has a p-type AlGaN-based semiconductor. Each semiconductor layer in the n-type and the active layers is an epitaxially grown layer having a surface on which multi-step terraces parallel to the (0001) plane are formed. The n-type layer has first Ga-rich regions which include n-type AlGaN regions in which an AlGaN composition ratio is an integer ratio of Al7Ga5N12, and each extending direction of the stratiform regions is inclined with respect to the upper surface of the n-type layer.