GaN HEMT Cascode With Integrated Schottky Diode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
GaN-based switching devices lack an intrinsic body diode, making them inefficient for normally OFF operations and requiring reliance on slow and inefficient internal body diodes of Si FETs, which complicates drive circuitry and reduces efficiency.
Innovation Solution
A depletion mode GaN-based HEMT FET is cascaded with a high-speed FET semiconductor switch and a Schottky diode, either as separate components or monolithically integrated, to create an enhancement mode FET device that bypasses the internal body diode, allowing for efficient normally OFF operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a depletion mode GaN FET is used, then higher power density and breakdown voltage are achieved, but the device operates as normally ON which reduces efficiency and complicates drive circuitry
Solution Approach 1:
The device is segmented into two functional parts: a depletion mode GaN FET for high voltage switching and a separate fast recovery body diode structure. This segmentation allows the GaN FET to maintain its high power density advantages while the separate diode provides efficient reverse recovery characteristics, resolving the contradiction between power density and operational efficiency.
Solution Approach 2:
A separate fast recovery body diode structure is introduced as an intermediary element to handle the reverse recovery function. This intermediary diode works in parallel with the GaN FET, providing efficient reverse recovery while allowing the GaN FET to operate in depletion mode for high power density, thus resolving the efficiency contradiction.
2Strength
If a depletion mode GaN FET is used, then higher breakdown voltage is achieved, but normally ON operation requires more complicated and expensive drive circuitry
Solution Approach 1:
A separate fast recovery body diode structure is introduced as an intermediary element to handle the reverse recovery function. This intermediary diode works in parallel with the GaN FET, providing efficient reverse recovery while allowing the GaN FET to operate in depletion mode for high power density, thus resolving the efficiency contradiction.
3Ease of operation
If an internal body diode of Si FET is used, then normally OFF operation is achieved, but the switching speed is slow and efficiency is reduced
Solution Approach 1:
The body diode parameters are changed by introducing a separate fast recovery body diode structure with optimized doping and geometry. This separate diode structure provides fast reverse recovery characteristics while enabling normally OFF operation, thus resolving the contradiction between operational mode and switching speed through parameter optimization.
Solution Approach 2:
The device is segmented into two functional parts: a depletion mode GaN FET for high voltage switching and a separate fast recovery body diode structure. This segmentation allows the GaN FET to maintain its high power density advantages while the separate diode provides efficient reverse recovery characteristics, resolving the contradiction between power density and operational efficiency.
4Ease of manufacture
If GaN FET and higher speed switching device are monolithically integrated, then easier assembly and packaging is achieved, but manufacturing complexity increases
Solution Approach 1:
The GaN FET and fast recovery body diode structures are merged into a single monolithic device on the same substrate. This merging integrates both functions into one package, simplifying assembly and packaging while the shared substrate and interconnections manage the integration complexity, resolving the contradiction between ease of manufacture and device complexity.
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
This configuration significantly reduces reverse recovery current and time, enhancing efficiency and simplifying packaging and assembly, while enabling easier integration and higher power density in power semiconductor devices.
Implementation Method 1
the higher speed switching device comprises a high speed FET semiconductor switch arranged or connected in parallel with a Schottky diode
Data Source
AI summary
A power semiconductor device is provided that includes a depletion mode (normally ON) main switching device cascoded with a higher speed switching device, resulting in an enhancement mode (normally OFF) FET device for switching power applications. The main switching device comprises a depletion mode GaN-based HEMT (High Electron Mobility Transistor) FET that does not include an intrinsic body diode. In one or more embodiments, the higher speed switching device comprises a high speed FET semiconductor switch arranged or connected in parallel with a Schottky diode. The high speed FET semiconductor switch may comprise a Si FET, GaN FET or any other type of FET which possesses higher speed switching capabilities and a lower voltage than that of the GaN-based HEMT FET. In some embodiments, the GaN-based HEMT FET and the higher speed switching device (i.e., the FET and Schottky diode) may be monolithically integrated on the same substrate.