HEMT-BJT Compound Transistor Structure for Low Knee Voltage
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Solution Overview
Problem
High Electron Mobility Transistors (HEMTs) face limitations due to high knee voltage, which restricts the available output power and power-added efficiency (PAE) in devices.
Innovation Solution
A compound semiconductor device is proposed, integrating a HEMT with a bipolar junction transistor (BJT) on a common substrate, where the BJT assists the HEMT's output, reducing the knee voltage requirements and enhancing current carrying capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If HEMT is used for high power operation, then high electron mobility and high-frequency performance are improved, but high knee voltage increases and limits available output power
Solution Approach 1:
The patent combines HEMT and BJT into a single integrated device structure where the HEMT provides high electron mobility for high-frequency operation while the BJT provides low knee voltage characteristics. The two transistor types are merged such that they share common regions (emitter of BJT serves as source of HEMT, collector of BJT serves as drain of HEMT), enabling the device to simultaneously achieve low knee voltage and high output power capability.
2Speed
If HEMT structure is adopted, then high-frequency performance is improved, but high knee voltage reduces power capacity and power-added efficiency
Solution Approach 1:
The integrated HEMT-BJT structure merges the high-frequency capabilities of HEMT with the power handling capabilities of BJT. The device maintains the high electron mobility of HEMT for high-frequency operation while incorporating BJT's low knee voltage特性 to enhance power capacity and power-added efficiency, resolving the trade-off between frequency performance and power capacity.
3Use of energy by moving object
If single bipolar transistor configuration is used, then low knee voltage is achieved, but current carrying capability and input impedance are limited
Solution Approach 1:
The patent merges BJT's low knee voltage特性 with HEMT's high current carrying capability. The integrated structure enables the device to achieve both low knee voltage (inherited from BJT) and enhanced current carrying capability (enhanced by HEMT's high electron mobility), surpassing the limitations of single bipolar transistor configuration.
Solution Approach 2:
The device employs a composite transistor structure combining two different transistor types (HEMT and BJT) into a single integrated device. This composite approach leverages the complementary strengths of each transistor type to achieve performance characteristics that neither transistor type could achieve alone, specifically low knee voltage combined with high current carrying capability.
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 integrated device achieves high current carrying capability with low knee voltage requirements, resulting in higher drain current and input impedance compared to single bipolar transistor configurations, making it suitable for applications requiring high power and high-frequency performance.
Implementation Method 1
A HEMT has a high-power density due to high electron mobility provided by an underlying two-dimensional electron gas (2-DEG) channel. The 2-DEG channel has a high electron mobility, which allows for efficient current flow at high voltages.
Implementation Method 2
A compound semiconductor configuration comprises a HEMT and a bipolar junction transistor (BJT) grown on a common substrate. The BJT assists the HEMT's output thereby providing low knee voltage requirements for the overall device.
Data Source
AI summary
A compound transistor comprises a plurality of electrodes, a first semiconductor structure, and a second semiconductor structure. The electrodes include a source, a gate, and a drain of a first transistor. The first semiconductor structure is electrically connected to the plurality of electrodes and includes a barrier layer and a first channel layer. The second semiconductor structure includes a second channel layer, a buffer layer, and a substrate layer arranged such that the buffer layer is sandwiched between the second channel layer and the substrate layer. The second transistor structure supports the first semiconductor structure such that a connecting layer is arranged between the first and the second semiconductor structures. A source electrode is electrically connected to the second channel layer such that the source of the first transistor forms a base of a second transistor, and the source electrode forms a collector of the second transistor.