GaN HEMT Bypass Transistor for Leakage Current Management

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Solution Overview

Problem

Cascode circuits with GaN high electron mobility transistors (HEMTs) experience increased leakage current and dynamic on-state resistance over time, limiting their operational lifetime, especially when compared to Si metal-insulator-semiconductor field-effect transistors (MISFETs), necessitating a solution to reduce degradation and extend the lifespan of GaN HEMTs.

Innovation Solution

Incorporating a bypass transistor in parallel with the principal drive high-side transistor, designed to have higher leakage current than the GaN HEMT, which reduces the leakage current flowing through the GaN HEMT, thereby slowing the increase in dynamic on-state resistance and extending its operational lifetime.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the circuit is designed to operate at a higher drive current, then the power output is improved, but the leakage current increases

Engineering Contradiction:

Improvepower outputVSAvoidleakage current

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The high-side transistor function is segmented into two parallel transistors: a principal drive transistor for power delivery and a bypass transistor for leakage current management. This segmentation allows each transistor to be optimized for its specific function while working together to solve the leakage problem at high drive currents

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bypass transistor acts as an intermediary element that provides an alternative current path. By positioning this transistor in parallel with the principal drive transistor, it mediates the leakage current away from the main power path, allowing high drive current operation while maintaining low leakage

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the drive current is increased, then the circuit performance is improved, but the degradation of GaN HEMT increases over time

Engineering Contradiction:

Improvecircuit performanceVSAvoidGaN HEMT lifetime

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The transistor function is segmented to separate the high-stress power delivery role from the leakage management role. The principal drive transistor handles power delivery while the bypass transistor manages leakage, reducing cumulative stress and degradation on the GaN HEMT structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The leakage current, which is normally a harmful effect that degrades the GaN HEMT, is converted into a beneficial function by routing it through the bypass transistor. This transforms the harmful leakage into a protective mechanism that actually extends device lifetime by reducing stress on the principal drive transistor

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9985022B2Electronic device including a cascode circuit having principal drive and bypass transistors

Publication Date: 2018.05.29 SEMICON COMPONENTS IND LLC

AI summary

An electronic device can include a first transistor including a first gate electrode; and a second transistor including a second gate electrode. The first and second transistors can be electrically connected in a parallel arrangement, wherein the transistors have one or more different characteristics. For example, gate length, barrier layer thickness, gate-to-drain distance, leakage current, on-state electron density, or the like may be different between the transistors. The difference in characteristics can help to reduce degradation and improve the lifetime of the first transistor.