Multi-Layer LED Structure for Suppressing p-Layer Impurity Diffusion
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Solution Overview
Problem
Semiconductor light-emitting elements face deterioration when exposed to high temperatures during the growth process of subsequent light-emitting element portions, particularly due to diffusion of n-type impurities like Si into p-type nitride semiconductor layers.
Innovation Solution
A method involving the formation of a protective film containing an n-type impurity over the p-side nitride semiconductor layer, with an upper n-type semiconductor layer forming a tunnel junction, which reduces impurity diffusion and maintains p-type conductivity, allowing for the growth of additional light-emitting element portions without significant deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective film containing n-type impurity is formed over the p-side nitride semiconductor layer, then impurity diffusion is reduced and p-type conductivity is maintained, but the device structure becomes more complex
Solution Approach 1:
An upper n-type semiconductor layer is introduced as an intermediary between the protective film and the p-side nitride semiconductor layer. This intermediate layer acts as a diffusion barrier that prevents n-type impurities from the protective film from diffusing into the p-type layer, while still allowing the protective film to perform its protective function. The tunnel junction formed at the interface provides both electrical isolation and physical separation, effectively blocking impurity diffusion pathways.
Solution Approach 2:
The structure is segmented into distinct functional layers: the protective film, the upper n-type semiconductor layer, and the p-side nitride semiconductor layer. Each layer performs a specific function - the protective film provides environmental protection, the upper n-type layer serves as a diffusion barrier and forms a tunnel junction, and the p-side layer maintains p-type conductivity. This segmentation allows each component to be optimized independently for its specific purpose.
2Productivity
If multiple light-emitting element portions are grown on a single substrate, then productivity is improved, but the earlier formed light-emitting element portions are exposed to high temperatures again causing deterioration
Solution Approach 1:
The upper n-type semiconductor layer is formed in advance before the protective film is applied. This preliminary formation of the diffusion barrier layer ensures that when subsequent high-temperature processing is performed for growing additional light-emitting element portions, the previously formed layers are already protected from impurity diffusion. The tunnel junction is established beforehand to prevent future deterioration during multi-step growth processes.
Solution Approach 2:
The upper n-type semiconductor layer serves as a cushioning barrier that protects the p-side nitride semiconductor layer from the harmful effects of high-temperature processing. By placing this protective layer beforehand, the structure is prepared to withstand subsequent thermal processing without suffering from impurity diffusion that would otherwise occur during the growth of additional light-emitting element portions.
3Quantity of substance
If the protective film is heated at high temperature, then impurity diffusion is enhanced, but this causes deterioration of the light-emitting element portion without the protective measures
Solution Approach 1:
The upper n-type semiconductor layer converts the potentially harmful high-temperature heating process into a beneficial outcome. While heating enhances impurity diffusion in general, the presence of the upper n-type layer with its tunnel junction actually prevents n-type impurities from reaching the p-side layer. The heating process can now proceed to ensure good electrical contact and junction formation without causing the harmful deterioration that would occur in unprotected structures.
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 approach effectively reduces the deterioration of the first light-emitting element portion during subsequent heating steps, enabling the formation of multiple light-emitting element portions on a single substrate with maintained electrical conductivity and structural integrity.
Implementation Method 1
The first p-side nitride semiconductor layer and the upper n-type semiconductor layer form a tunnel junction
Implementation Method 2
an upper n-type semiconductor layer forming a tunnel junction, which reduces impurity diffusion and maintains p-type conductivity
Implementation Method 3
heating at least the upper n-type semiconductor layer and the protective film
Data Source
AI summary
A light-emitting device includes: a first light-emitting element portion including: an n-side nitride semiconductor layer, a first light-emitting layer disposed on the n-side nitride semiconductor layer, and a first p-side nitride semiconductor layer disposed on the first light-emitting layer; a second light-emitting element portion including: a second light-emitting layer disposed on the n-side nitride semiconductor layer, and a second p-side nitride semiconductor layer disposed on the second light-emitting layer; an n-side electrode connected to the n-side nitride semiconductor layer; a first p-side electrode disposed on the first p-side nitride semiconductor layer via an upper n-type semiconductor layer disposed on the first p-side semiconductor layer; and a second p-side electrode connected to the second p-side nitride semiconductor layer. A composition of the second light-emitting layer is different from a composition of the first light-emitting layer.