GaN Semiconductor Device Impurity Diffusion Prevention Layer
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Solution Overview
Problem
Gallium nitride (GaN)-based semiconductor lasers face issues with high threshold current density due to p-type impurity diffusion, which reduces device reliability and lifespan, as the impurity can diffuse to the active layer during temperature changes and operational use.
Innovation Solution
A semiconductor device structure is implemented with an active layer, an overflow prevention layer, a second semiconductor layer, and an impurity diffusion prevention layer, all formed from GaN-based compound semiconductors, where the impurity diffusion prevention layer has a smaller band gap than the other layers to prevent p-type impurity diffusion to the active layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GaAlN layer doped with p-type impurity is arranged close to an active layer to suppress electron overflow, then electron overflow is suppressed, but p-type impurity diffuses to the active layer causing increased threshold current density and reduced reliability
Solution Approach 1:
An undoped GaN layer is introduced as an intermediary barrier between the p-type doped GaAlN layer and the active layer. This undoped layer prevents p-type impurity diffusion to the active layer while maintaining the electron overflow suppression function of the doped GaAlN layer, thus resolving the contradiction between reliability improvement and impurity diffusion prevention
2Productivity
If the GaAlN layer is positioned close to the active layer to improve device performance, then device performance is improved, but the threshold current density increases due to impurity diffusion during operation
Solution Approach 1:
The undoped GaN layer acts as a diffusion barrier that prevents p-type impurity migration to the active layer during device operation. This maintains low threshold current density while allowing the doped GaAlN layer to remain close to the active layer for optimal device performance
3Ease of manufacture
If the growth temperature is increased to grow GaN/GaAlN layer, then the layer is successfully grown, but heat damage defects are introduced to the crystal growth layer
Solution Approach 1:
The crystal growth process is segmented into distinct temperature stages: first growing the active layer and undoped GaN layer at lower temperatures (700-800°C) to maintain crystal quality, then increasing temperature to grow the doped GaAlN layer. This segmentation allows each layer to be grown at its optimal temperature, preventing heat damage defects
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 effectively prevents p-type impurity diffusion to the active layer, enhancing the reliability and lifespan of GaN-based semiconductor devices by maintaining a lower threshold current density and ensuring consistent optical output over extended periods.
Implementation Method 1
p-type impurity diffusion, which reduces device reliability and lifespan, as the impurity can diffuse to the active layer during temperature changes and operational use
Data Source
AI summary
A semiconductor device has an active layer, a first semiconductor layer of first conductive type, an overflow prevention layer disposed between the active layer and the first semiconductor layer, which is doped with impurities of first conductive type and which prevents overflow of electrons or holes, a second semiconductor layer of first conductive type disposed at least one of between the active layer and the overflow prevention layer and between the overflow prevention layer and the first semiconductor layer, and an impurity diffusion prevention layer disposed between the first semiconductor layer and the active layer, which has a band gap smaller than those of the overflow prevention layer, the first semiconductor layer and the second semiconductor layer and which prevents diffusion of impurities of first conductive type.