GaN HEMT Peak Amplifier Gain Profile Optimization
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Solution Overview
Problem
Doherty amplifiers using GaN HEMTs do not achieve expected efficiency improvements due to similar gain profiles between carrier and peak amplifiers, leading to high d.c. component in output signals and reduced efficiency, especially when the peak amplifier operates in the back-off region.
Innovation Solution
A compound semiconductor device with specific layer structures and doping concentrations is used for the peak amplifier, including a lower electron transport layer of non-doped GaN, a lower electron supply layer of n-type AlGaN, an upper electron transport layer of non-doped GaN, and an upper electron supply layer of n-type Al0.25Ga0.75N, with optimized atomic ratios and doping concentrations to differentiate the gain profiles and reduce idle current, thereby improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional GaN HEMTs are used in both carrier and peak amplifiers, then the amplifier can operate at high breakdown voltage, but the gain profiles remain similar leading to high d.c. component and reduced efficiency
Solution Approach 1:
The patent applies different layer structures and doping concentrations to the peak amplifier HEMT compared to the carrier amplifier HEMT. Specifically, the peak amplifier uses an AlGaN electron supply layer with specific Al composition ratio (0.25-0.40) and doping concentration (1×10^18 to 1×10^19 atoms/cm³) to create a differentiated gain profile that reduces d.c. component while maintaining high breakdown voltage capability.
Solution Approach 2:
The patent changes key parameters of the HEMT structure for the peak amplifier, including Al composition ratio in the electron supply layer (0.25-0.40), doping concentration (1×10^18 to 1×10^19 atoms/cm³), and layer thickness (5-20 nm), to optimize the gain profile and reduce the d.c. component in the output signal, thereby improving efficiency without sacrificing breakdown voltage.
2Use of energy by stationary object
If the peak amplifier is biased with small idle current, then d.c. consumption is reduced, but the gain profile remains similar to carrier amplifier causing large d.c. component in output
Solution Approach 1:
The patent modifies the local structure of the peak amplifier HEMT by implementing an AlGaN electron supply layer with specific composition ratio (0.25-0.40) and doping concentration (1×10^18 to 1×10^19 atoms/cm³), which creates a differentiated gain profile that suppresses the d.c. component in output signals even when operated with small idle current, thereby simultaneously reducing d.c. consumption and improving efficiency.
Solution Approach 2:
The patent changes the Al composition ratio to 0.25-0.40 and doping concentration to 1×10^18 to 1×10^19 atoms/cm³ in the electron supply layer of the peak amplifier HEMT, which fundamentally alters the gain profile to enable efficient operation with small idle current by suppressing the d.c. component in the output signal.
3Power
If carrier amplifier operates in saturated state, then large output power is achieved, but forward gate leak current increases disabling distortion compensation
Solution Approach 1:
The patent introduces an AlGaN electron supply layer with specific composition ratio (0.25-0.40) and doping concentration (1×10^18 to 1×10^19 atoms/cm³) as an intermediary structure between the gate and the channel in the peak amplifier HEMT. This layer acts as a mediator that suppresses forward gate leak current while allowing the carrier amplifier to operate in saturated state for large output power, thereby preserving distortion compensation 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 solution enhances the efficiency of the Doherty amplifier by suppressing gain and reducing the d.c. component of the output power at small input signals, achieving up to 42% efficiency at the distortion compensation collapsed point, compared to 35% with conventional HEMTs.
Implementation Method 1
a lower electron supply layer disposed over the lower electron transport layer and made of compound semiconductor material doped to n-type
Implementation Method 2
an upper electron supply layer disposed over the upper electron transport layer and made of n-type compound semiconductor material
Implementation Method 3
a gate electrode disposed over the upper electron supply layer between the source electrode and the drain electrode
Implementation Method 4
a lower electron transport layer made of compound semiconductor material; an upper electron transport layer disposed over the lower electron supply layer
Data Source
AI summary
A lower electron supply layer is disposed over a lower electron transport layer made of compound semiconductor. The lower electron supply layer is made of n-type compound semiconductor having an electron affinity smaller than that of the lower electron transport layer. An upper electron transport layer is disposed over the lower electron supply layer. The upper electron transport layer is made of compound semiconductor having a doping concentration lower than that of the lower electron supply layer or non-doped compound semiconductor. An upper electron supply layer is disposed over the upper electron transport layer. The upper electron supply layer is made of n-type compound semiconductor having an electron affinity smaller than that of the upper electron transport layer. A source and drain electrodes are disposed over the upper electron supply layer. A gate electrode is disposed over the upper electron supply layer between the source and drain electrodes.