Deep-UV LED N-Electrode Stack for Low-Resistance Ohmic Contact
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Solution Overview
Problem
Achieving ohmic contact between the n-side contact layer and n-electrode in nitride semiconductor light emitting elements for deep ultraviolet wavelength range is challenging, despite efforts to lower forward voltage and improve emission efficiency.
Innovation Solution
A nitride semiconductor light emitting element structure is developed, featuring an n-side contact layer with a Ti layer, a Si-containing Al alloy layer, and a Ta or W layer, which successively form good ohmic contact and increase light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple n-side contact layer structure is used, then the device complexity is reduced, but the contact resistance increases and ohmic contact cannot be achieved
Solution Approach 1:
The n-electrode is divided into three distinct layers (Ti layer, Si-containing Al alloy layer, and Ta or W layer) to perform different functions: the Ti layer provides initial contact, the Si-containing Al alloy layer reduces contact resistance through silicide formation, and the Ta or W layer provides stable ohmic contact. This segmentation allows each layer to be optimized for its specific function, achieving low contact resistance while maintaining a manageable structure.
Solution Approach 2:
The patent uses a composite electrode structure combining different materials (Ti, Al-Si alloy, Ta/W) to achieve properties that no single material could provide alone. The Si-containing Al alloy layer acts as an intermediate composite layer that facilitates ohmic contact between the Ti layer and the n-side contact layer, while the Ta or W layer provides long-term stability.
2Use of energy by moving object
If the forward voltage is reduced to improve emission efficiency, then the energy utilization is improved, but achieving ohmic contact becomes more difficult
Solution Approach 1:
The patent changes the compositional parameters of the electrode layers, specifically incorporating Si into the Al alloy layer at controlled concentrations. This parameter change enables the formation of low-resistance silicide compounds at the interface, allowing ohmic contact to be achieved even when the forward voltage is reduced to improve emission efficiency.
3Reliability
If a multi-layer n-electrode structure is implemented, then the ohmic contact is achieved, but the manufacturing process complexity increases
Solution Approach 1:
The Si-containing Al alloy layer is deposited in advance before the final Ta or W layer, creating a prepared interface that facilitates subsequent ohmic contact formation. This preliminary action of placing the Si-containing layer first enables easier manufacturing of the final electrode structure with optimized contact properties.
Data Source
AI summary
A method of manufacturing a nitride semiconductor light-emitting element configured to emit deep ultraviolet light includes: providing a semiconductor structure comprising:an n-side semiconductor layer comprising an n-side contact layer comprising aluminum, gallium, and nitrogen, a p-side semiconductor layer, and an active layer between the n-side semiconductor layer and the p-side semiconductor layer; forming an n-side electrode, which comprises forming, successively from an n-side contact layer side: a first layer located above the n-side contact layer and comprising a titanium layer, a second layer located above the first layer and comprising a silicon-containing aluminum alloy layer, and a third layer located above the second layer and comprising a tantalum layer and/or a tungsten layer; and heating the n-side electrode.