HEMT Transistor Barrier Recess for Gate Corner Field Reduction
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Solution Overview
Problem
High electron mobility transistor (HEMT) devices experience hot carrier degradation and reliability issues due to high electric fields at the gate corner, leading to instability in threshold voltage and dynamic on-resistance during high voltage switching applications.
Innovation Solution
A transistor device design featuring a substrate with a buffer layer, source, drain, and gate terminals, where a barrier layer with a recess is formed between the gate and drain, and a passivation layer extends into the recess, reducing the gate corner electric field and hot electron generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a typical HEMT device structure is used with gate, source, and drain terminals arranged over the buffer layer, then the device can achieve high-frequency and high-power switching performance, but a high electric field is formed at the gate corner during switching which accelerates electrons and causes hot carrier degradation
Solution Approach 1:
The barrier layer is segmented by introducing a recess structure laterally between the gate terminal and drain terminal. This segmentation creates a distinct region with different electrical characteristics that reduces the electric field concentration at the gate corner, thereby mitigating hot carrier generation while preserving the overall high-power switching capability of the device
Solution Approach 2:
The recess in the barrier layer acts as an intermediary structure between the gate terminal and drain terminal. This intermediate region modifies the electric field distribution and electron transport characteristics, reducing the acceleration of electrons at the critical gate corner region while maintaining the device's power switching performance
2Productivity
If the HEMT device operates in high voltage switching mode with high drain bias, then high current can flow through the 2DEG channel, but hot electrons are generated and trapped in the hetero-junction materials causing degradation in threshold voltage stability and dynamic on-resistance
Solution Approach 1:
The recess structure introduces local quality variation in the barrier layer, creating a region with different band structure and electron transport properties. This local modification reduces electron acceleration and hot carrier generation in the critical region near the gate corner, thereby improving threshold voltage stability while allowing high current flow in other regions of the device
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 design effectively suppresses hot carrier generation and enhances the stability of the device's threshold voltage and on-resistance, improving reliability and reducing gate degradation, while maintaining high voltage switching performance.
Implementation Method 1
Due to a difference in the conduction band energy of the materials, electrons may diffuse from the wide bandgap material to the narrow bandgap material to form a conducting channel commonly known as a two-dimensional electron gas (2DEG) channel
Implementation Method 2
In operation, the HEMT device may be turned on by applying an appropriate gate voltage. During this switching, the HEMT device usually goes through a semi-on state where its drain bias is high (for example, about 600V) and where current starts to flow through the 2DEG channel
Data Source
AI summary
A transistor device may be provided, including a substrate; a buffer layer arranged over the substrate; a source terminal, a drain terminal, and a gate terminal arranged over the buffer layer; a barrier layer arranged over the buffer layer; and a passivation layer arranged over the barrier layer. The gate terminal may be arranged laterally between the source terminal and the drain terminal, the barrier layer may include a recess laterally between the gate terminal and the drain terminal, a part of the gate terminal may be arranged over the passivation layer and the passivation layer may extend into the recess of the barrier layer.