Al-Delta Layer in UV Light Emitting Device
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Solution Overview
Problem
UV light emitting devices using nitride semiconductors face significant deterioration in luminous efficacy due to absorption of UV light by n-type and p-type nitride semiconductor layers, which reduces hole injection efficiency and lateral hole dispersibility.
Innovation Solution
Incorporating an Al-delta layer with a higher band-gap in the hole injection direction to enhance hole injection efficiency through a two-dimensional hole gas effect, and using a p-type semiconductor layer structure with an Al-delta layer, hole injection layer, and contact layers to manage Al content and doping concentration for improved hole injection and dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Al is contained in the nitride semiconductor layer to increase band-gap for UV light emission, then UV light emission capability is improved, but hole injection efficiency deteriorates due to increased ionization energy
Solution Approach 1:
The patent applies local quality by creating an Al-delta layer with localized high Al content (higher than both the hole injection layer and contact layer) at a specific position between them. This localized region provides high band-gap for UV emission while the surrounding layers maintain lower Al content to facilitate hole injection, thus resolving the contradiction between UV emission capability and hole injection efficiency.
Solution Approach 2:
The patent changes the Al content parameter spatially by creating a gradient structure where the Al-delta layer has higher Al content than adjacent layers. This parameter variation allows the structure to simultaneously achieve high band-gap regions for UV emission and lower band-gap regions for efficient hole injection, resolving the contradiction through controlled compositional changes.
2Reliability
If conventional alternating p-type layers with different doping concentrations are used to provide lateral hole dispersion, then some hole dispersion is achieved, but hole dispersibility deteriorates significantly and cannot suppress deterioration sufficiently
Solution Approach 1:
The patent uses local quality by positioning the Al-delta layer with high Al content at a specific location between the hole injection layer and contact layer. This localized high-band-gap region creates effective potential barriers that confine and disperse holes laterally, achieving superior hole dispersibility compared to conventional alternating layer structures while maintaining high hole injection efficiency.
Solution Approach 2:
The patent creates a composite structure combining the hole injection layer, Al-delta layer with higher Al content, and contact layer with lower Al content. This composite material structure integrates the benefits of high band-gap (for hole confinement and dispersibility) and low band-gap (for hole injection), achieving both high hole injection efficiency and superior lateral hole dispersibility simultaneously.
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 Al-delta layer structure improves hole injection efficiency and lateral hole dispersibility, reducing forward voltage and maintaining high luminous efficacy by uniformly injecting holes into the active layer, while the high doping concentration in the Al-delta layer further enhances these effects.
Implementation Method 1
Incorporating an Al-delta layer with a higher band-gap in the hole injection direction to enhance hole injection efficiency through a two-dimensional hole gas effect
Implementation Method 2
The Al-delta layer may have a thickness allowing holes to enter the active layer by tunneling therethrough, preferably 20 nm or less
Data Source
AI summary
A UV light emitting device is disclosed. The UV light emitting device includes: a substrate; an n-type semiconductor layer disposed on the substrate; an active layer disposed on then-type semiconductor layer; a hole injection layer disposed on the active layer and comprising Al; an Al-delta layer disposed on the hole injection layer and comprising Al; and a first p-type contact layer disposed on the Al-delta layer and having a higher doping concentration of p-type dopants than the hole injection layer, wherein the first p-type contact layer has a lower Al content than the hole injection layer, a band-gap of the first p-type contact layer is lower than or equal to energy of light emitted from the active layer, and the Al-delta layer has a higher Al content than the hole injection layer and allows holes to enter the active layer by tunneling therethrough.