GaN Drain Contact Structure for Back-Gating Shielding
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Solution Overview
Problem
Gallium nitride (GaN)-based transistors suffer from the back-gating effect, leading to reliability issues such as dynamic drain-source on-state resistance (RDSON) and safe operating area (SOA) degradation due to the depletion of the 2DEG channel, especially at high voltages, which results in transistor failure.
Innovation Solution
The design incorporates an extended drain contact structure that extends into the GaN layer, shielding the vertical electrical field and preventing back-gating, thereby reducing channel depletion and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional drain contact structure is used in GaN-based transistors, then the device structure is simple and manufacturing is easier, but the back-gating effect causes channel depletion leading to reliability degradation and transistor failure at high voltages
Solution Approach 1:
The drain contact structure is extended vertically into the GaN layer beneath the AlGaN barrier layer, transitioning from a surface-level contact to a deep-substrate contact. This dimensional change allows the drain contact to reach and shield the 2DEG channel directly, preventing the back-gating effect while maintaining structural simplicity in the horizontal plane.
Solution Approach 2:
The extended drain contact acts as an intermediary conductive path between the drain electrode and the 2DEG channel. By extending through the AlGaN layer into the GaN layer, it provides a direct electrical connection that shields the channel from voltage-induced depletion, mediating the electric field distribution to prevent reliability degradation.
2Reliability
If the drain contact extends into the GaN layer to shield the 2DEG channel, then back-gating effect is reduced and reliability improves, but the manufacturing process becomes more complex requiring precise etching and alignment
Solution Approach 1:
The mask layer is formed with a pre-defined opening pattern that specifies the exact location and depth of the drain contact extension. This preliminary patterning step establishes the precise alignment requirements before etching, allowing the drain contact to be accurately positioned to extend through the AlGaN layer and into the GaN layer without requiring complex real-time alignment during manufacturing.
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 extended drain contact structure effectively shields the 2DEG channel from the back-gating effect, reducing the depletion of the channel and improving the reliability of GaN-based transistors by preventing premature failure and maintaining performance at high voltages.
Implementation Method 1
The design incorporates an extended drain contact structure that extends into the GaN layer, shielding the vertical electrical field and preventing back-gating
Data Source
AI summary
A semiconductor device is described herein. The semiconductor device comprises a silicon substrate layer. The semiconductor device comprises a first semiconductor layer comprising a gallium nitride layer, the first semiconductor layer disposed over the silicon substrate layer. The semiconductor device comprises a second semiconductor layer disposed on the first semiconductor layer, the second semiconductor layer comprising an aluminum gallium nitride layer. The semiconductor device comprises a first drain contact extending through the second semiconductor layer and extending into the first semiconductor layer.