Compound Semiconductor Device With Uniformly Doped Carrier Supply Layer
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Solution Overview
Problem
Existing high electron mobility transistors (HEMTs) face performance limitations due to impurity diffusion from planar doped supply layers, which complicates production and degrades high-frequency characteristics and mobility, with previous solutions like reducing thermal history or adding In to GaAs layers either compromising reliability or increasing complexity.
Innovation Solution
A compound semiconductor device structure is implemented with a uniformly doped carrier supply layer on the lower side of the channel layer and a planar doped layer on the upper side, omitting Al mixed crystal layers to suppress impurity diffusion and maintain high-frequency performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a planar doped supply layer is used to supply carriers at high concentration, then carrier supply efficiency is improved, but impurity diffusion increases causing performance degradation
Solution Approach 1:
The patent applies local quality by using planar doped supply layer only on the upper side of the channel layer where high carrier concentration is needed, while using uniformly doped supply layer on the lower side where impurity diffusion would harmfully affect the channel. This spatial differentiation of doping strategies optimizes carrier supply while preventing impurity contamination.
Solution Approach 2:
The patent segments the carrier supply function into two distinct supply layers with different doping characteristics. The upper supply layer uses planar doping for high concentration carrier supply, while the lower supply layer uses uniform doping to avoid impurity diffusion into the channel. This segmentation allows each layer to perform its specific function optimally.
2Object-generated harmful factors
If In is added to GaAs or AlGaAs layer to reduce lattice distortion, then impurity diffusion is suppressed, but device complexity increases
Solution Approach 1:
The patent changes the doping parameter (uniform vs. planar doping) and material composition parameters (Al content in AlGaAs barrier layer) to achieve impurity diffusion suppression. By optimizing these parameters, the patent eliminates the need for additional In-containing layers, thereby suppressing impurity diffusion while maintaining simple device structure.
3Reliability
If Al mixed crystal layer is formed to improve mobility, then carrier mobility is improved, but source series resistance increases degrading high frequency characteristics
Solution Approach 1:
The patent applies local quality by forming AlGaAs barrier layers with specific Al content (10-30%) only in the regions where high carrier concentration is needed (near the channel), while maintaining GaAs contact layer with high carrier concentration at the contact region. This spatial differentiation optimizes mobility where needed while minimizing resistance at contact regions.
Solution Approach 2:
The patent changes the material composition parameter (Al content) and carrier concentration parameter to achieve optimal balance between mobility and resistance. By controlling Al content in AlGaAs barrier layer and carrier concentration in contact layer, the patent improves mobility while keeping source series resistance low.
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 effectively suppresses impurity diffusion, improves mobility by 31%, and stabilizes production without increasing source series resistance or degrading high-frequency characteristics, using a simpler structure.
Implementation Method 1
locally high concentration impurity doping makes the impurity more likely to diffuse, and it is known that the impurity enters the channel layer from the planar doped supply layer
Implementation Method 2
reduction of thermal history through lowering the temperature and reducing the time period of epitaxial growth has been proposed
Data Source
AI summary
A compound semiconductor device includes: a substrate; and a buffer layer, a first carrier supply layer, a first spacer layer, a channel layer, a second spacer layer, a second carrier supply layer, and a contact layer provided in order on the substrate, wherein the first carrier supply layer is a uniformly doped layer in which an impurity is uniformly doped, the second carrier supply layer is a planar doped layer in which an impurity is locally doped, and no Al mixed crystal layer having higher resistance values than the first and second spacer layers is provided between the buffer layer and the first spacer layer and between the second spacer layer and the contact layer.