Crank-Shaped GaAs Multigate Transistor Field Strength
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Solution Overview
Problem
Conventional crank-shaped multigate field effect transistors face challenges in achieving sufficient dielectric strength due to differences in recess widths and electric field concentration at bent portions, which affect the transistor's operating characteristics and dielectric strength.
Innovation Solution
The design incorporates a non-active region around the perpendicularly and parallelly extending portions of the gate electrodes and a continuously extending active region between the gate electrodes, with a potential clamp electrode to stabilize the potential and reduce electric field concentration, and an arc-shaped bent portion to minimize dielectric strength reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching is used to form recesses in the n-type GaAs layer, then the recessed structure is formed, but the etching rate differs in different directions causing different widths between perpendicularly and parallelly extending portions of the recesses
Solution Approach 1:
The patent applies local quality by making different portions of the gate electrode have different functions. The perpendicularly extending portion is designed to have a longer length than the parallelly extending portion, compensating for the narrower recess width in the perpendicular direction. This local differentiation allows each portion to be optimized for its specific geometric constraints while maintaining overall device performance.
2Area of stationary object
If crank-shaped gate electrodes are used to reduce FET area, then the device size is reduced, but electric field concentration at bent portions reduces dielectric strength
Solution Approach 1:
The patent changes the geometric parameters of the gate electrode by making the perpendicularly extending portion longer than the parallelly extending portion. This parameter adjustment compensates for the electric field concentration effect at the bent portions by optimizing the voltage distribution across different gate sections, thereby maintaining dielectric strength while preserving the area reduction benefits of the crank shape.
3Area of stationary object
If all portions of crank-shaped gate electrodes function as gates, then gate area is maximized, but perpendicularly and parallelly extending portions cannot both have sufficient dielectric strength due to different recess widths
Solution Approach 1:
The patent implements local quality by assigning different functional roles and dimensions to different portions of the gate electrode. The perpendicularly extending portion is made longer to compensate for the narrower recess width, while the parallelly extending portion maintains its original dimensions. This localized optimization ensures that each gate portion achieves sufficient dielectric strength despite the anisotropic recess geometry, while the entire crank-shaped structure continues to provide maximum gate area coverage.
Data Source
AI summary
A field effect transistor includes a pair of ohmic electrodes and an n-type GaAs layer between the pair of ohmic electrodes and having recesses. Crank-shaped gate fingers are located within the recesses of the n-type GaAs layer between the pair of ohmic electrodes, and each crank-shaped gate finger includes perpendicular-extending portions and parallel-extending portions relative to the [0, 1, 1] crystal orientation of the n-type GaAs layer. The portion of the n-type GaAs layer between the gate fingers continuously extends from input ends of the gate electrodes to terminal ends of the gate electrode. A non-active region is located around each perpendicular-extending portion of the gate fingers.