Backward Diode Junction Capacitance Reduction via Doping Gradients
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Solution Overview
Problem
Existing MMICs with backward diodes face challenges in achieving low pn junction capacitance and high cutoff frequency due to high junction capacitance, which affects MMW detection sensitivity.
Innovation Solution
The semiconductor device incorporates a structure with multiple n-type semiconductor layers having different compositions and band gaps, aligned to reduce doping concentration and junction capacitance, allowing for easier tunneling current flow and lower resistance, thereby increasing cutoff frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a backward diode with high doping concentration is used to achieve low resistance, then resistance is reduced, but pn junction capacitance increases
Solution Approach 1:
The patent applies local quality by creating distinct regions with different doping concentrations within the semiconductor structure. Specifically, it uses a first semiconductor layer with first doping concentration and a second semiconductor layer with second doping concentration, where the doping concentrations differ to optimize local electrical properties. This allows low resistance in contact regions while maintaining low capacitance in the junction region.
Solution Approach 2:
The patent employs parameter changes by varying the doping concentration parameter across different semiconductor layers. The first semiconductor layer has a first doping concentration optimized for low resistance, while the second semiconductor layer has a second doping concentration optimized for low capacitance. This parameter variation resolves the contradiction between resistance and capacitance requirements.
2Use of energy by moving object
If doping concentration is increased to reduce resistance, then resistance decreases, but cutoff frequency is affected
Solution Approach 1:
The patent applies local quality by creating distinct regions with different doping concentrations within the semiconductor structure. Specifically, it uses a first semiconductor layer with first doping concentration and a second semiconductor layer with second doping concentration, where the doping concentrations differ to optimize local electrical properties. This allows low resistance in contact regions while maintaining low capacitance in the junction region.
Solution Approach 2:
The patent employs parameter changes by varying the doping concentration parameter across different semiconductor layers. The first semiconductor layer has a first doping concentration optimized for low resistance, while the second semiconductor layer has a second doping concentration optimized for low capacitance. This parameter variation resolves the contradiction between resistance and capacitance requirements.
3Ease of operation
If a Schottky diode is used for detection, then detection function is provided, but detection sensitivity is insufficient near 0 V bias
Solution Approach 1:
The patent applies composite materials by combining different semiconductor materials with different band gaps to form a heterojunction structure. The first semiconductor layer and second semiconductor layer are made of different materials that create a type II heterojunction, enabling enhanced detection sensitivity near 0 V bias while maintaining proper detection function. This composite structure resolves the contradiction between detection function and detection sensitivity.
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 configuration enhances MMW detection sensitivity by reducing junction capacitance and maintaining low resistance, improving the overall performance of MMW detectors.
Implementation Method 1
the backward diode has the so-called type II heterojunction in a flat band state, and the energy of the conduction band of an n-type semiconductor layer is higher than that of the valence band of a p-type semiconductor layer
Data Source
AI summary
A semiconductor device includes a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and third and fourth semiconductor layers of the first conductivity type formed between the first and second semiconductor layer. The first, the third, the fourth, and the second semiconductor layers are coupled in this order. A band gap of the third semiconductor layer is narrower than that of the first semiconductor layer, and a band gap of the fourth semiconductor layer is narrower than that of the third semiconductor layer.