Composite E-Mode GaN HEMT Structure for Short-Circuit Current Clamping
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Solution Overview
Problem
GaN HEMTs are prone to short-circuit phenomena during high-voltage operations due to high drain voltage and current, leading to heat generation and potential device failure.
Innovation Solution
A method is proposed to improve the short-circuit capability of E-mode GaN HEMTs by depositing metal in the active region between the gate and source, forming a composite structure that combines a conventional E-mode GaN HEMT with a depletion-mode GaN HEMT, thereby reducing the saturation current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If GaN HEMT operates at high voltage, then power density and efficiency are improved, but short-circuit capability deteriorates due to high drain voltage and current causing heat generation
Solution Approach 1:
The patent segments the gate structure into multiple regions with different threshold voltages. The gate is divided into a first gate region with a first threshold voltage and a second gate region with a second threshold voltage, where the first threshold voltage is lower than the second threshold voltage. This segmentation allows different parts of the gate to activate at different voltage levels, enabling progressive control of the 2DEG channel to limit short-circuit current while maintaining high power operation capability
Solution Approach 2:
The patent applies local quality by creating regions with different electrical properties within the gate structure. The first gate region has different doping concentration or thickness compared to the second gate region, resulting in different threshold voltages. This local differentiation enables the gate to exhibit different control characteristics in different regions, allowing the device to maintain high power density while improving short-circuit capability through localized threshold voltage control
2Reliability
If saturation current density is reduced to improve short-circuit capability, then short-circuit withstand time is extended, but device conduction capability deteriorates
Solution Approach 1:
The patent implements dynamic control of the 2DEG channel through the multi-region gate structure. During normal operation, the full gate voltage controls the channel for high conduction capability. During short-circuit conditions, the lower threshold voltage region activates first to progressively limit the current. This dynamic response allows the device to switch between high conduction mode and current limitation mode based on operating conditions
Solution Approach 2:
The patent prepares the gate structure in advance with regions of different threshold voltages during fabrication. This preliminary configuration ensures that during a short-circuit event, the current limitation action occurs automatically and rapidly without requiring external intervention. The lower threshold voltage region is pre-positioned to activate first, providing immediate current limiting protection
Data Source
AI summary
Embodiments of the present application provides a method for improving the short-circuit capability of an enhancement-mode (E-mode) GaN HEMT and its device structure. This is achieved by depositing metal in the active region between the gate and the source, adjacent to the source region of a conventional E-mode GaN HEMT, the metal is directly connected with the source of the conventional E-mode GaN HEMT. The conventional E-mode GaN HEMT is combined with a gate-source-shorted depletion-mode (D-mode) GaN HEMT to form a complete E-mode GaN HEMT with improved short-circuit capability. By clamping the saturation current of the complete device through the D-mode GaN HEMT, the saturation current density of the E-mode GaN HEMT can be reduced, and the purpose of improving the short-circuit capability is finally realized.