Single Voltage PHEMT Power Device with Double Recessed Gate
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Solution Overview
Problem
PHEMT power devices require a negative gate voltage bias for operation, increasing chip complexity and manufacturing costs, and existing devices are unsatisfactory in the X frequency band (8.0 to 12.0 GHz) and unusable in the Ka frequency band (18 to 40 GHz) when operating with a single voltage supply.
Innovation Solution
An optimized PHEMT power device structure with a semi-insulating substrate, epitaxial substrate, and double recessed gate geometry, utilizing wide band-gap semiconductors and advanced epitaxial growth technologies to achieve improved RF performance, linearity, and power-added efficiency, allowing operation up to 40 GHz with a single voltage supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative gate voltage bias is used for PHEMT operation, then the device can operate properly, but chip complexity and manufacturing costs increase
Solution Approach 1:
The patent changes the electrical parameters of the device by making the gate electrode electrically connected to the source electrode, transforming the gate voltage from a separate controlled parameter to a fixed parameter (0V). This eliminates the need for a dedicated negative voltage supply circuit while maintaining proper device operation through the optimized epitaxial layer structure that enables single-voltage-supply mode operation.
2Device complexity
If existing PHEMT devices operate with a single voltage supply, then chip complexity is reduced, but RF performance in X and Ka frequency bands becomes unsatisfactory
Solution Approach 1:
The patent applies local quality by creating non-uniform doping distributions in specific epitaxial layers. The first and second doped GaAs layers have different doping concentrations (3×10^18 atoms/cm³ and 1×10^19 atoms/cm³ respectively), and the AlGaAs layers have spatially varying aluminum compositions. This local optimization of material properties enables the device to achieve satisfactory RF performance in X and Ka bands while operating with a single voltage supply.
Solution Approach 2:
The patent uses composite materials by combining multiple semiconductor layers with different bandgaps and electrical properties. The epitaxial substrate includes GaAs, AlGaAs, and InGaAs layers forming a heterostructure that combines the advantages of wide-bandgap materials (for high breakdown voltage and thermal stability) with narrow-bandgap materials (for high electron mobility and RF performance), enabling single-voltage-supply operation at high frequencies.
3Adaptability or versatility
If the operating frequency is increased to millimeter wave range, then application scope is expanded, but device performance requirements become more stringent
Solution Approach 1:
The patent segments the epitaxial structure into multiple functional layers, each with specific thicknesses and doping profiles. The channel region is divided into sections with different AlGaAs barrier layers (30 nm and 5 nm thick) and doped GaAs layers, allowing independent optimization of each segment for high-frequency operation. This segmentation enables precise control of electron transport properties required for millimeter wave applications.
Solution Approach 2:
The patent performs preliminary actions by pre-optimizing the epitaxial layer structure during manufacturing with specific doping concentrations and layer thicknesses designed for high-frequency operation. The doped GaAs layers are positioned and dimensioned in advance to create the desired electric field distribution and electron concentration profiles, enabling the device to operate at millimeter wave frequencies without requiring complex external biasing circuits.
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 optimized PHEMT power device achieves higher linearity, breakdown voltage, and power-added efficiency, enabling satisfactory operation in high-frequency digital wireless communications up to 40 GHz with a single voltage supply, reducing chip complexity and manufacturing costs.
Implementation Method 1
an InGaAs electron transit layer 15... The higher frequency response of PHEMTs are currently finding use in millimeter wave communications (40 Gb/s) and radar systems
Implementation Method 2
the condition of ensuring that free electrons in the conductive channel are physically separated from ionized donors. This solution allows for a significant reduction in ionized impurity scattering, enhancing electron mobility
Implementation Method 3
a gate electrode formed on the Schottky layer to extend through the contact layer... formed in the narrow recess and in Schottky contact with the Schottky layer
Implementation Method 4
an optimized PHEMT epitaxial layer structure... thin-film technology development adequate for high frequency functions
Data Source
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AI summary
Disclosed herein is a pseudomorphic high electron mobility transistor (PHEMT) power device (1) including a semi-insulating substrate (2); an epitaxial substrate (3) formed on the semi-insulating substrate (2) a contact layer (19). The contact layer (19) includes a lightly doped contact layer (20) formed on the Schottky layer (18), and a highly doped contact layer (21) formed on the lightly doped contact layer (20) and having a doping concentration higher than the lightly doped contact layer (20). The PHEMT power device (1) further includes a- wide recess (23) formed to penetrate the highly doped contact layer (21) and a narrow recess (24) formed in the wide recess (23) to penetrate the lightly doped contact layer (20). The gate electrode (6) is formed in the narrow recess (24) and in Schottky contact with the Schottky layer (18).