Vertical III-V Trench FET Shielding Against Early Breakdown
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Solution Overview
Problem
Vertical gallium nitride transistors face early electrical breakdown due to high electrical fields at the base of the trench structure, which can cause voltage to extend through to the gate electrode, compromising their operational reliability.
Innovation Solution
A shielding structure with a second conductivity type is introduced laterally adjacent to the trench structure, extending vertically into the drift region, to shield the base from electrical fields and prevent voltage leakage to the gate electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical HEMT structure with a V-shaped trench is used to achieve low ON resistance and high breakdown voltage, then the transistor can exploit the full capability of the III-V heterostructure, but high electrical fields at the base of the trench cause early electrical breakdown and voltage leakage to the gate electrode
Solution Approach 1:
A shielding structure with a third conductivity type is introduced as an intermediary element between the drift region and the trench base. This shielding structure acts as a mediator that redirects electrical fields away from the vulnerable trench base, preventing direct interaction between the high electrical fields and the gate electrode while maintaining the vertical HEMT's low ON resistance characteristics
Solution Approach 2:
The shielding structure is positioned in advance at the base of the trench to preemptively counteract the harmful electrical fields before they can cause breakdown or extend to the gate electrode. By establishing this protective barrier beforehand, the design prevents early electrical breakdown without requiring changes to the core vertical HEMT structure
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
The shielding structure effectively increases the transistor's resistance and prevents early electrical breakdown, ensuring reliable operation by redirecting the electrical field away from the trench base.
Implementation Method 1
a III-V heterostructure for forming a two-dimensional electron gas at a boundary surface of the III-V heterostructure
Implementation Method 2
a shielding structure that is situated laterally adjacent to the at least one side wall of the trench structure and extends vertically into the drift region... to shield the base from electrical fields
Data Source
AI summary
A vertical field effect transistor, including a drift region having a first conductivity type, a trench structure on or above the drift region, a shielding structure, and a source/drain electrode. The trench structure includes at least one side wall at which a field effect transistor (FET) channel region is formed. The FET channel region includes a III-V heterostructure for forming a two-dimensional electron gas at a boundary surface of the III-V heterostructure. The shielding structure is situated laterally adjacent to the at least one side wall of the trench structure and extends vertically into the drift region or vertically further in the direction of the drift region than the trench structure. The shielding structure has a second conductivity type that differs from the first conductivity type. The source/drain electrode is electroconductively connected to the III-V heterostructure of the trench structure and to the shielding structure.