GaN HEMT Co-Doping for High Carrier Concentration
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Solution Overview
Problem
Traditional doping methods for GaN layers in HEMT devices fail to achieve high maximum active carrier concentration while maintaining a smooth surface/interface morphology, leading to lattice strain and morphology degradation.
Innovation Solution
Co-doping of n-type gallium nitride (GaN) layers with silicon (Si) and germanium (Ge) to achieve a carrier concentration of at least 1×10^20 cm−3 with a root mean square (RMS) surface roughness no greater than 2 nm, enhancing the upper limit of n-type active carrier concentration and maintaining smooth surface/interface morphology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional doping methods (Si alone or Ge alone) are used to increase carrier concentration, then the maximum active carrier concentration is improved, but the surface/interface morphology deteriorates due to lattice strain
Solution Approach 1:
The patent applies composite doping by combining silicon and germanium dopants in the GaN layer. This composite approach allows the material to achieve higher carrier concentrations while maintaining smooth surface morphology, as the combined dopant system balances the electrical properties and structural integrity better than single dopant systems
Solution Approach 2:
The patent changes the doping parameters by introducing co-doping with specific silicon and germanium concentrations. By adjusting the dopant composition ratios and concentrations, the patent achieves an optimal balance between carrier concentration enhancement and surface morphology preservation, extending the upper limit of n-type active carrier concentration to at least 1×10^20 cm−3 while maintaining RMS surface roughness no greater than 2 nm
2Reliability
If higher carrier concentration is achieved through traditional doping, then electrical conductivity is improved, but lattice strain increases causing morphology degradation
Solution Approach 1:
The patent uses composite doping with silicon and germanium to achieve high carrier concentration while managing lattice strain. The combination of dopants creates a more balanced structural impact compared to single dopant systems, allowing electrical conductivity improvement without excessive lattice distortion
Solution Approach 2:
The patent applies local quality by distributing dopant atoms throughout the GaN layer in controlled concentrations. The co-doping approach creates localized regions with optimized dopant combinations that enhance electrical properties while maintaining overall lattice stability and preventing excessive strain accumulation
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 co-doped n-type GaN layers achieve higher carrier concentrations and improved surface smoothness, as evidenced by slower attenuation of X-ray reflectivity scan results, with reduced sheet resistivity and increased Hall mobility, effectively addressing the limitations of traditional doping methods.
Implementation Method 1
the n-type GaN layer is co-doped with silicon (Si) and germanium (Ge) that provide a carrier concentration of at least 1×10^20 cm−3
Implementation Method 2
as evidenced by slower attenuation of X-ray reflectivity scan results
Data Source
AI summary
A high electron mobility transistor (HEMT) device with epitaxial layers that include a gallium nitride (GaN) layer co-doped with silicon (Si) and germanium Ge and a method of making the same is disclosed. The HEMT device includes a substrate with epitaxial layers over the substrate. An n-type gallium nitride (GaN) layer is disposed on an interface surface of the epitaxial layers, wherein the n-type GaN layer is co-doped with silicon (Si) and germanium (Ge) that provide a carrier concentration of at least 1×1020 cm−3 and a root mean square (RMS) surface roughness that is no greater than 2 nm for a contact surface of the n-type GaN layer that is interfaced with the interface surface of the epitaxial layers.