Nitride Semiconductor Structure with Resistivity Gradient
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Solution Overview
Problem
Devices such as transistors produced using nitride semiconductor layers suffer from current collapse due to carrier trapping at the surface or inside the transistor, leading to deteriorated switching properties, especially as the switching voltage increases.
Innovation Solution
A nitride semiconductor structure is developed with a semiconductor substrate having a surface region and internal region with specific resistivity values, where the surface region has a resistivity of 0.1 Ωcm or more and the internal region has a resistivity of 1000 Ωcm or more, and an epitaxial layer with a thickness of at least 1000 nm, formed using techniques like MOCVD, to control impurity diffusion and extend the depletion layer depth, thereby reducing electric field strength and preventing current collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If nitride semiconductor layers are formed over a silicon substrate, then high-frequency and high-power device performance is improved, but current collapse occurs due to carrier trapping at the surface or inside the transistor
Solution Approach 1:
The patent applies local quality by creating a non-uniform resistivity distribution within the silicon substrate, with a high-resistivity internal region (1000 Ωcm or more) and a lower-resistivity surface region (0.1 Ωcm or more). This spatial differentiation allows the internal region to provide high-quality carrier transport for high-power performance while the surface region manages carrier trapping effects, thereby preventing current collapse.
Solution Approach 2:
The patent changes the resistivity parameter of the silicon substrate by creating distinct regions with different resistivity values. The internal region maintains resistivity of 1000 Ωcm or more to minimize carrier trapping, while the surface region has resistivity of 0.1 Ωcm or more to manage surface effects. This parameter differentiation resolves the contradiction between achieving high-power performance and preventing current collapse.
2Power
If the switching voltage is increased, then the power handling capability is improved, but the switching properties deteriorate due to carrier trapping
Solution Approach 1:
The patent uses local quality by designing the silicon substrate with spatially varying resistivity: the internal region (1000 Ωcm or more) provides a high-quality environment for high-voltage operation and power handling, while the surface region (0.1 Ωcm or more) manages surface-related trapping effects that would otherwise degrade switching properties at high voltages.
Solution Approach 2:
The surface region of the silicon substrate acts as an intermediary layer that mediates between the high-voltage internal region and the external environment. It manages carrier trapping at the surface, thereby protecting the switching properties while allowing the internal region to maintain high power handling capability at increased switching voltages.
3Reliability
If the resistivity of the semiconductor substrate is increased to extend the depletion layer depth, then the electric field strength is reduced and current collapse is prevented, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating a silicon substrate with non-uniform resistivity distribution, where the internal region has high resistivity (1000 Ωcm or more) to extend the depletion layer and reduce electric field strength for current collapse prevention, while the surface region has lower resistivity (0.1 Ωcm or more) for practical manufacturing and device operation.
Solution Approach 2:
The patent changes the resistivity parameter of the silicon substrate by establishing distinct regions with different resistivity values. This parameter differentiation allows the internal region to provide extended depletion layer depth and reduced electric field strength for reliable operation, while maintaining manufacturability through the surface region with optimized resistivity.
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 structure effectively prevents current collapse and enhances the switching properties of transistors and diodes by maintaining a stable electric field and voltage distribution, improving the overall performance and yield of nitride semiconductor devices.
Implementation Method 1
the surface region has a resistivity of 0.1 Ωcm or more, and the internal region has a resistivity of 1000 Ωcm or more
Implementation Method 2
extend the depletion layer depth, thereby reducing electric field strength
Implementation Method 3
high-concentration and high-mobility carriers in its interface by spontaneous polarization and piezoelectric polarization are generated
Implementation Method 4
high-concentration and high-mobility carriers in its interface by spontaneous polarization and piezoelectric polarization are generated
Data Source
AI summary
A nitride semiconductor structure of the present disclosure comprises a semiconductor substrate, and a layer formed over the semiconductor substrate and comprising plural nitride semiconductor layers. The semiconductor substrate has, from a side thereof near the layer comprising the plural nitride semiconductor layers, a surface region and an internal region in this order. The surface region has a resistivity of 0.1 Ωcm or more, and the internal region has a resistivity of 1000 Ωcm or more.