UV Light Emitting Device Multi-Layer Hole Injection
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Solution Overview
Problem
Conventional ultraviolet light emitting devices experience reduced optical efficiency due to the hole injection layer functioning as a light absorber in the specific ultraviolet region, leading to suboptimal performance.
Innovation Solution
A multi-layer hole injection layer comprising AlxGa1-xN and GaN layers is introduced between the active and second conductive semiconductor layers to prevent ultraviolet light absorption and induce compressive strain, improving hole injection efficiency and reducing operating voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single-layer GaN hole injection layer is used, then hole injection is facilitated, but ultraviolet light is absorbed reducing optical efficiency
Solution Approach 1:
The hole injection layer is divided into multiple sub-layers with different materials (AlGaN layers with varying Al compositions and GaN layers). This segmentation allows each sub-layer to perform specialized functions: AlGaN layers with higher Al content provide compressive strain for improved hole injection, while GaN layers with lower absorption coefficient transmit UV light more effectively, thus resolving the contradiction between hole injection efficiency and optical efficiency.
Solution Approach 2:
The hole injection layer uses a composite structure combining AlGaN and GaN materials. This composite approach leverages the complementary properties of both materials: AlGaN provides the necessary strain for hole injection while GaN provides better optical transmission in the UV range. The composite structure achieves both improved hole injection and reduced light absorption simultaneously.
2Ease of operation
If AlGaN layer with high Al composition is used to induce compressive strain, then hole injection efficiency improves, but light absorption increases
Solution Approach 1:
Different regions of the hole injection layer have different Al compositions tailored to their specific functions. The lower AlGaN layer has higher Al content (0.5<x<0.7) to provide strong compressive strain for hole injection, while the upper AlGaN layer has lower Al content (0.3<y<0.5) to reduce light absorption. This local quality variation resolves the contradiction by optimizing each region for its primary function.
Solution Approach 2:
The Al composition parameter is varied across different layers and positions within the hole injection layer. By changing the Al composition from higher values in the lower layer to lower values in the upper layer, the structure achieves both compressive strain for hole injection and reduced optical absorption. This parameter optimization resolves the contradiction between injection efficiency and optical efficiency.
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 multi-layer hole injection layer effectively enhances optical efficiency and reduces operating voltage by minimizing ultraviolet light absorption and improving Mg injection efficiency.
Implementation Method 1
the hole injection layer induces a compressive strain to improve efficiency of Mg, thereby improving an operating voltage
Implementation Method 2
When forward voltage is applied to the light emitting device, electrons of an N layer are combined with holes of a P layer, so that energy corresponding to band gap energy between a conduction band and a valance band may be diverged. The energy is mainly emitted in the form of heat or light. In the case of the light emitting device, the energy is diverged in the form of light.
Data Source
AI summary
A light emitting device, according to one embodiment, may comprise: a substrate; a first conductive semiconductor layer disposed on the substrate; an active layer disposed on the first conductive semiconductor layer and generating an ultraviolet light; a second conductive semiconductor layer disposed on the active layer; and a hole injection layer disposed between the active layer and the second conductive semiconductor layer and comprising a first layer comprising AlxGa1-xN (0<x≤1) and a second layer comprising GaN. The embodiment has the hole injection layer to be multi-layered, thereby having the effect of effectively preventing the absorption of ultraviolet light.