Buried P-Type Layer Activation via Trench Exposure
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Solution Overview
Problem
The existing process for manufacturing high-brightness III-nitride light emitting devices, such as LEDs, requires an anneal in a hydrogen-free atmosphere to activate p-type layers, limiting device design and preventing the formation of devices with buried p-type layers or tunnel junctions, as hydrogen cannot diffuse through n-type III-nitride materials.
Innovation Solution
The solution involves growing a semiconductor structure with a buried p-type layer and forming trenches that expose portions of this layer, allowing hydrogen to diffuse out during annealing, thereby activating the p-type region without covering it, and subsequently filling or passivating the trenches to enable metal contact formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the p-type layer is grown using conventional MOCVD process with ammonia, then the p-type material can be formed, but hydrogen forms complexes with magnesium dopant that deactivate the p-type character, reducing dopant concentration and device efficiency
Solution Approach 1:
The patent divides the processing into distinct stages: first growing the p-type layer with magnesium dopant during MOCVD, then performing a separate post-growth annealing treatment in a hydrogen-free atmosphere. This segmentation allows the layer to be formed initially, then activated separately to remove hydrogen complexes, thereby resolving the contradiction between forming the layer and maintaining its electrical activity.
Solution Approach 2:
The patent applies preliminary doping action by incorporating magnesium dopant during the MOCVD growth phase, before the harmful hydrogen complexes fully form. The subsequent annealing then activates this pre-positioned dopant by removing hydrogen, ensuring the p-type character is established before degradation occurs.
2Reliability
If an anneal is performed in a hydrogen-free atmosphere to activate p-type layers, then hydrogen-magnesium complexes are broken and p-type character is activated, but this limits device design and prevents formation of devices with buried p-type layers or tunnel junctions
Solution Approach 1:
The patent applies local quality by performing selective annealing treatments on specific regions or layers. By controlling the annealing conditions and duration, only the intended p-type layers are activated while preserving the ability to have buried p-type layers or tunnel junctions in other regions, thus maintaining device design flexibility while achieving necessary activation.
Solution Approach 2:
The patent introduces dynamic control over the annealing process parameters (temperature, time, atmosphere composition) to achieve selective activation. This dynamic approach allows different portions of the device structure to be treated differently, enabling complex device architectures with buried p-type layers or tunnel junctions while still activating where needed.
3Adaptability or versatility
If the p-type layer is covered by other layers to enable device design flexibility, then buried p-type layers or tunnel junctions can be formed, but hydrogen cannot diffuse out during annealing, preventing activation of the p-type layer
Solution Approach 1:
The patent performs preliminary activation annealing before depositing subsequent layers that would block hydrogen diffusion. By activating the p-type layer first when the structure is still open, hydrogen can escape during annealing. After activation, additional layers are deposited to create the desired buried structure, thus achieving both activation and design flexibility.
Solution Approach 2:
The patent inverts the conventional sequence by activating the p-type layer before covering it with subsequent layers. Instead of growing the p-type layer, covering it, then attempting activation (which fails), the process grows the layer, activates it while accessible, then covers it to create the buried structure. This inversion resolves the contradiction between coverage and activation.
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 activates the p-type layers, enabling the formation of devices with buried p-type layers or tunnel junctions, improving radiative efficiency by reversing the internal electric field and allowing for more flexible device designs.
Implementation Method 1
forming trenches that expose portions of this layer, allowing hydrogen to diffuse out during annealing
Implementation Method 2
After growth of the p-type material, the structure is annealed in order to break the hydrogen-magnesium complex by driving off the hydrogen
Data Source
AI summary
In a method according to embodiments of the invention, a semiconductor structure including a III-nitride light emitting layer disposed between a p-type region and an n-type region is grown. The p-type region is buried within the semiconductor structure. A trench is formed in the semiconductor structure. The trench exposes the p-type region. After forming the trench, the semiconductor structure is annealed.