GaN HEMT Compensation Structure for Low Forward Bias Diode
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Solution Overview
Problem
Conventional GaN/AlGaN high electron mobility transistors (HEMTs) face challenges in accurately controlling doping, leading to difficulties in designing high-blocking mode and low forward bias diodes, which results in increased switching losses due to high reverse recovery time and unstable Schottky diodes.
Innovation Solution
The integration of a compensation structure with a different band gap between two III-V semiconductor regions, forming two conductive channels, one controllable by the gate and the other not, to achieve a low forward bias diode with a stable threshold voltage and high current drive capability, utilizing Al-containing layers to shape the energy barrier and separate carrier reservoirs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pseudo-body diode is formed in conventional GaN/AlGaN HEMT, then the device can provide body diode function, but the forward bias voltage becomes too high (around 3V) and increases with stronger off-state bias
Solution Approach 1:
The patent divides the single channel into two separate channels: a first conductive channel controlled by the gate and a second conductive channel not controlled by the gate. This segmentation allows the second channel to provide a low forward bias path for the body diode while the first channel maintains transistor functionality, resolving the contradiction between body diode function and forward bias voltage.
Solution Approach 2:
The patent introduces a compensation structure with different band gap as an intermediary element between the two III-V semiconductor regions. This compensation structure shapes the energy barrier to achieve the desired low forward bias voltage while maintaining stable threshold voltage, acting as a mediator that reconciles the conflicting requirements.
2Use of energy by moving object
If a lateral Schottky diode is integrated with HEMT to achieve low forward bias, then forward bias voltage is reduced, but device area increases and manufacturing cost increases
Solution Approach 1:
The patent merges the body diode function with the transistor structure by forming the second conductive channel within the existing device architecture. This integration allows the body diode to share the same physical space as the transistor, achieving low forward bias without increasing device area or requiring separate Schottky diode fabrication.
Solution Approach 2:
The patent creates a multi-functional device where the second conductive channel serves dual purposes: providing a low forward bias path for body diode operation and contributing to overall device current drive capability. This universal approach eliminates the need for separate dedicated diode structures.
3Adaptability or versatility
If doping is used to control electrical properties in GaN/AlGaN HEMT, then device performance can be tailored, but doping control accuracy is difficult and represents a major drawback
Solution Approach 1:
The patent changes the fundamental parameter used to control electrical properties from doping concentration to polarization effects and band gap engineering. By utilizing the different band gap material properties and polarization charges inherent in III-V semiconductor structures, the device achieves performance tailoring without relying on difficult-to-control doping processes.
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 approach reduces the forward bias voltage to less than 1V, stabilizes the diode operation, and enhances current drive capability while avoiding the area penalty and cost increase associated with traditional Schottky diode integration, thereby improving switching behavior and reducing switching losses.
Implementation Method 1
a compensation structure 110 with a different band gap than the upper and lower III-V semiconductor buffer regions 116, 108
Implementation Method 2
The main electrical properties of a typical GaN/AlGaN device are controlled via polarization charges
Data Source
AI summary
A high electron mobility transistor includes a source, a gate and a drain, a first III-V semiconductor region, and a second III-V semiconductor region below the first III-V semiconductor region. The high electron mobility transistor further includes a compensation structure interposed between the first and second III-V semiconductor regions so that the first and second III-V semiconductor regions are spaced apart from one another by the compensation structure. The compensation structure has a different band gap than the first and second III-V semiconductor regions.