Gate Electrode Foot Penetration for High Voltage Stability
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Solution Overview
Problem
Conventional field effect transistors face challenges in achieving high breakdown voltage and cutoff frequency while maintaining reliable high voltage operation, particularly in high-frequency electronic devices.
Innovation Solution
The design includes a field effect transistor with a gate electrode having a foot portion and a head portion, where the foot portion penetrates the active layer and substrate, and the head portion has a wider width, along with an insulating layer between the gate and active layers, to reduce electric fields and enhance breakdown voltage and cutoff frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gate electrode structure is used, then the device structure is simple, but the breakdown voltage is low and high voltage operation is unstable
Solution Approach 1:
The gate electrode is segmented into multiple distinct portions: a foot portion penetrating the active layer, a middle portion, and a head portion on the capping layer. This segmentation allows each portion to serve specific functions - the foot portion reduces leakage current by extending into the active layer, the middle portion provides transition, and the head portion maintains wide coverage for low resistance. This segmented structure enables stable high voltage operation without excessive complexity.
Solution Approach 2:
The gate electrode structure extends in multiple dimensions: vertically through penetration of the active layer (foot portion) and horizontally through varying width (narrower foot portion, wider head portion). This multi-dimensional configuration allows the gate to simultaneously achieve low leakage current (via vertical extension) and low resistance (via horizontal width), resolving the contradiction between reliability and structural simplicity.
2Reliability
If the gate electrode penetrates deeper into the active layer, then the leakage current is reduced, but the manufacturing precision requirement increases
Solution Approach 1:
The gate electrode is divided into a foot portion that penetrates the active layer and a head portion that remains on the capping layer. This segmentation concentrates the penetration function specifically in the foot portion, allowing controlled deep penetration where it provides leakage reduction, while the head portion maintains a simpler, more precisely controllable structure on the surface. The insulating layer between gate and active layer further defines the penetration boundary precisely.
3Reliability
If a nitride semiconductor structure is used, then the cutoff frequency and breakdown voltage are improved, but the lattice mismatch causes structural modification requirements
Solution Approach 1:
The device structure employs local quality differentiation with an insulating layer positioned specifically between the gate electrode and active layer, and between the gate electrode and capping layer. This localized insulating structure manages the lattice mismatch effects in critical regions without requiring modification of the entire nitride semiconductor layer structure, thereby maintaining the high cutoff frequency and breakdown voltage benefits while controlling structural complexity.
Data Source
AI summary
A field effect transistor includes an active layer and a capping layer sequentially stacked on a substrate, and a gate electrode penetrating the capping layer and being adjacent to the active layer. The gate electrode includes a foot portion adjacent to the active layer and a head portion having a width greater than a width of the foot portion. The foot portion of an end part of the gate electrode has a width less than a width of the head portion of another part of the gate electrode and greater than a width of the foot portion of the another part of the gate electrode. The foot portion of the end part of the gate electrode further penetrates the active layer so as to be adjacent to the substrate.