AlGaN Barrier Oxygen Doping for HEMT Sheet Resistance
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Solution Overview
Problem
High sheet resistance in high electron mobility transistors (HEMTs) using AlGaN as the barrier layer is a challenge due to strain-induced cracks and impurity scattering, limiting the manufacturing process options when InAlN is used, which affects the device's performance and drain current.
Innovation Solution
Doping oxygen into the AlGaN barrier layer with a concentration greater than or equal to 5.0×10^18 cm^-3 and forming non-doped AlGaN layers between GaN and oxygen-doped AlGaN layers to reduce strain and prevent crack formation, thereby lowering sheet resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If InAlN is used in the barrier layer to enable high output, then drain current increases, but sheet resistance becomes high due to In desorption at high processing temperatures
Solution Approach 1:
The patent changes the material composition parameter by substituting InAlN with AlGaN in the barrier layer, which has different thermal stability characteristics. This parameter change allows the device to maintain low sheet resistance at high processing temperatures while still achieving high drain current through optimized AlGaN composition and thickness
Solution Approach 2:
The patent uses a simpler AlGaN material system instead of the more complex InAlN, which is more susceptible to thermal degradation. This substitution with a more thermally stable material prevents In desorption and maintains consistent electrical properties throughout the manufacturing process
2Reliability
If AlGaN is used as the barrier layer with high Al composition to reduce sheet resistance, then sheet resistance decreases, but strain-induced cracks occur due to lattice constant difference
Solution Approach 1:
The patent applies local quality by creating a graded Al composition profile in the barrier layer, where the Al content varies gradually rather than being uniform. This gradual transition reduces the strain gradient and prevents crack formation while maintaining low sheet resistance in the regions where high Al content is present
Solution Approach 2:
The patent uses a composite structure combining multiple AlGaN layers with different Al compositions and thicknesses. This composite approach allows optimization of each layer's properties to balance strain management and electrical performance, preventing cracks while achieving low sheet resistance
3Productivity
If processing temperature is increased to improve manufacturing efficiency, then productivity increases, but In desorbs from InAlN causing sheet resistance to increase
Solution Approach 1:
The patent changes the material composition parameter by substituting InAlN with AlGaN in the barrier layer, which has different thermal stability characteristics. This parameter change allows the device to maintain low sheet resistance at high processing temperatures while still achieving high drain current through optimized AlGaN composition and thickness
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 approach effectively reduces sheet resistance and enhances drain current by preventing crack formation and reducing lattice constant stress, improving the overall performance of HEMTs.
Implementation Method 1
Doping oxygen into the AlGaN barrier layer with a concentration greater than or equal to 5.0×10^18 cm^-3
Implementation Method 2
piezoelectric polarization occurs due to strain that occurs in the AlGaN of the barrier layer caused by the difference of lattice constant between AlGaN and GaN. The piezoelectric polarization causes high concentration 2 DEG (Two-Dimensional Electron Gas) to be generated in the channel layer
Implementation Method 3
The use of InAlN in the barrier layer induces high concentration 2 DEG because InAlN has large spontaneous-polarization
Data Source
AI summary
A semiconductor device includes a substrate, a first semiconductor layer formed over the substrate, a second semiconductor layer formed over the first semiconductor layer, a third semiconductor layer formed over the second semiconductor layer, and a gate electrode, a source electrode, and a drain electrode that are formed over the third semiconductor layer. The first semiconductor layer includes a first nitride semiconductor. The second semiconductor includes a second nitride semiconductor. The third semiconductor layer includes a third nitride semiconductor. The concentration of oxygen included in the second semiconductor layer is less than 5.0×1018 cm−3. The concentration of oxygen included in the third semiconductor layer is greater than or equal to 5.0×1018 cm−3.