Reverse Blocking GaN HEMT Hybrid Drain Segmentation
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Solution Overview
Problem
The existing hybrid drain p-GaN RB-HEMTs have complex process steps and require precise control of etching thickness, leading to alignment errors and increased manufacturing difficulty, resulting in high forward turn-on voltage and low reverse blocking capability.
Innovation Solution
A p-GaN RB-HEMT structure with a hybrid drain formed by spaced p-GaN and Schottky contacts, where the p-GaN structures are formed synchronously with the gate structure, eliminating the need for recess etching and reducing processing complexity, while maintaining high reverse blocking capability and low forward turn-on voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-GaN-Schottky hybrid drain structure is used to improve reverse blocking capability, then reverse breakdown voltage increases, but forward turn-on voltage becomes too large
Solution Approach 1:
The drain structure is segmented into multiple p-GaN regions with different configurations: a first p-GaN structure forming a Schottky contact for reverse blocking, and a second p-GaN structure forming an ohmic contact for low forward voltage. This segmentation allows each region to perform its specialized function independently, resolving the contradiction between high reverse blocking and low forward turn-on voltage.
Solution Approach 2:
Different local regions of the drain are given different properties: the first p-GaN structure has Schottky contact characteristics for high breakdown voltage, while the second p-GaN structure has ohmic contact characteristics for low forward voltage. This local differentiation of contact types enables simultaneous optimization of both reverse blocking and forward conduction properties.
2Reliability
If recess etching is performed to form hybrid drain structure, then reverse breakdown voltage improves, but manufacturing complexity and difficulty increase
Solution Approach 1:
The p-GaN structures for both Schottky and ohmic contacts are formed simultaneously during the gate p-GaN formation process, before any etching operations. This preliminary formation of both drain structures in one step eliminates the need for subsequent complex recess etching processes to create the hybrid drain configuration.
Solution Approach 2:
The formation of the gate p-GaN structure and the drain p-GaN structures is merged into a single simultaneous process step. By combining these operations, the patent eliminates multiple sequential etching steps and reduces manufacturing complexity while achieving the desired hybrid drain structure.
3Device complexity
If multiple recess etching steps are performed for alignment, then hybrid drain structure is formed, but alignment errors occur leading to performance degradation
Solution Approach 1:
Both the gate p-GaN structure and drain p-GaN structures are formed in advance during the same epitaxial growth process, ensuring precise alignment is built-in from the beginning. This preliminary simultaneous formation eliminates subsequent alignment operations that would introduce errors.
Solution Approach 2:
The formation processes for gate and drain structures are merged into a single simultaneous operation. By combining these structures' formation in one step rather than separate steps requiring alignment, the patent eliminates alignment errors entirely while still achieving the complex hybrid drain configuration.
Data Source
AI summary
A reverse blocking gallium nitride (GaN) high electron mobility transistor includes, sequentially stacked from bottom to top, a substrate, a nucleation layer, a buffer layer, a barrier layer, a dielectric layer. The buffer layer and the barrier layer form a heterojunction structure. The barrier layer is provided with at least two p-GaN structures. The barrier layer is provided with a source metal at one end and a drain metal at the other end, source metal forms ohmic contact and drain metal forms Schottky contact with AlGaN barrier, respectively. In forward conduction, the two-dimensional electron gas below the spaced p-GaN structure connected to the drain metal is conductive, and a turn-on voltage of the device is low. During reverse blocking, the two-dimensional electron gas at the spaced p-GaN structure is rapidly depleted under reverse bias, to form a depletion region, so that the blocking capability of the device is improved.