GaN HEMT Buffer Doping for Fast Drain Current Recovery
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Solution Overview
Problem
Conventional semiconductor devices, such as high electron mobility transistors, exhibit poor linearity and unstable output power due to significant variations in gain over time, primarily because their drain current recovery time is too long, leading to unstable performance when used as amplifiers.
Innovation Solution
A semiconductor device with a GaN buffer layer doped with Fe or C is developed, which reduces the recovery time of the drain current to 5 seconds or less by neutralizing impurities and defects, thereby stabilizing the Fermi level and maintaining high linearity and consistent gain over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional buffer layer without Fe or C doping is used, then the carrier concentration is maintained at higher levels for better conductivity, but the recovery time becomes excessively long (more than 10 seconds) causing poor linearity and unstable gain
Solution Approach 1:
The patent applies parameter changes by doping the buffer layer with Fe or C at specific concentrations (Fe: 1×10^18-1×10^20/cm³ or C: 1×10^19-1×10^21/cm³) to fundamentally alter the electrical properties of the buffer layer. This doping changes the carrier concentration and creates deep level traps that accelerate carrier recombination, thereby reducing recovery time from over 10 seconds to 5 seconds or less while maintaining acceptable conductivity for amplifier operation
Solution Approach 2:
The patent converts the harmful effect of donor impurities and defects in the buffer layer (which cause long recovery times) into a beneficial effect by introducing Fe or C dopants. These dopants create deep level traps that actively capture and recombine excess carriers, transforming the buffer layer from a source of instability into a mechanism that accelerates recovery and stabilizes gain, thus converting what would be harmful carrier accumulation into a useful recovery mechanism
2Reliability
If the buffer layer has high donor impurity concentration, then the conductivity is improved, but the recovery time increases and linearity deteriorates
Solution Approach 1:
The patent introduces Fe or C dopants as intermediary elements in the buffer layer that mediate between the conflicting requirements of conductivity and recovery time. These dopants create deep level energy states that act as intermediate steps for carrier recombination, allowing carriers to recombine more rapidly through these intermediate states rather than requiring long times for natural recombination, thus enabling both acceptable conductivity and reduced recovery time
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 semiconductor device achieves stable power output with high linearity and minimal gain variation over time by reducing the recovery time of the drain current, enhancing its performance as an amplifier.
Implementation Method 1
The Fe in the buffer layer serves to deactivate donor impurities in the buffer layer and thereby reduce the carrier concentration of the layer
Implementation Method 2
stabilizing the Fermi level and maintaining high linearity and consistent gain over time
Data Source
AI summary
A semiconductor device includes a substrate, a buffer layer of GaN containing at least one of Fe and C and disposed on the substrate, a channel layer of GaN disposed on the buffer layer and through which electrons travel, an electron supply layer disposed on the channel layer and producing a two-dimensional electron gas in the channel layer, a gate electrode, a drain electrode, and a source electrode. Recovery time of a drain current of the semiconductor device is no more than 5 seconds, where the recovery time is defined as the period of time after the semiconductor device is stopped from outputting high frequency power until the change in the drain current, after the stopping of the semiconductor device, reaches 95% of the change in the drain current occurring during the first 10 seconds after the stopping of the semiconductor device.