Double Schottky-Barrier Diode for High-Order Frequency Multipliers
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Solution Overview
Problem
Current Schottky diode-based frequency multipliers face challenges in achieving high-order frequency multiplication due to increased ohmic contact loss and asymmetrical Capacitance-Voltage characteristics, making them unsuitable for terahertz applications.
Innovation Solution
A double Schottky-barrier diode structure is designed with a semi-insulating substrate, left and right mesas, and air-bridge fingers, where anode probes form Schottky contacts on a middle mesa with cathodes connected through a buffer layer, allowing for anti-series configuration and even symmetric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple diode dies are connected in anti-series or series configuration, then frequency multiplication capability is improved, but ohmic contact loss increases
Solution Approach 1:
The patent merges multiple Schottky diode structures into a single integrated device by forming two Schottky contacts on the same epitaxial layer, sharing common ohmic contacts (anode and cathode). This consolidation eliminates the need for separate ohmic contacts for each diode, thereby reducing total ohmic contact loss while maintaining the frequency multiplication capability through the anti-series connection of the two Schottky barriers within the unified structure.
Solution Approach 2:
The patent segments the single device into two distinct Schottky barrier regions (first and second Schottky contacts) with different contact areas, allowing independent optimization of each barrier's electrical characteristics. This segmentation enables the creation of asymmetric current-voltage characteristics necessary for efficient frequency multiplication while sharing common ohmic contacts to minimize resistive losses.
2Productivity
If multiple diode dies are connected in anti-series or series configuration, then frequency multiplication capability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple diode functions into a single integrated structure formed on one substrate, eliminating the need for separate diode dies and their associated packaging, interconnections, and alignment structures. The unified design with shared ohmic contacts and integrated Schottky barriers on a single epitaxial layer significantly reduces device complexity while achieving the desired frequency multiplication through internal anti-series configuration.
3Productivity
If multiple diode dies are connected in anti-series or series configuration, then frequency multiplication capability is improved, but even symmetry Capacitance-Voltage characteristics cannot be obtained
Solution Approach 1:
The patent intentionally creates asymmetric Schottky contacts with different contact areas (first Schottky contact has different area than second Schottky contact) to generate the necessary asymmetric current-voltage characteristics for frequency multiplication. This controlled asymmetry in contact geometry, combined with the anti-series electrical connection, produces the required even symmetry in Capacitance-Voltage characteristics that is essential for high-order frequency multiplier performance.
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 reduces series resistance and enhances frequency multiplication efficiency by eliminating even harmonics, making it suitable for high-order frequency multipliers with improved power capacity and simplified design.
Implementation Method 1
two anode probes respectively penetrate a passivation layer of the middle mesa, and contact an upper surface of an epitaxial layer of the middle mesa to form two Schottky contacts
Data Source
AI summary
A double Schottky-barrier diode includes a semi-insulating substrate, a left mesa formed by growth and etching on the semi-insulating substrate, a middle mesa formed by growth and etching on the semi-insulating substrate, a right mesa formed by growth and etching on the semi-insulating substrate, two anode probes and two air-bridge fingers. The two Schottky contacts are closely fabricated on the same mesa (middle mesa) in a back-to-back manner to obtain even symmetric C-V characteristics and odd symmetric I-V characteristics from the device level. The output of a frequency multiplier fabricated using the double Schottky-barrier diode only has odd harmonics, but no even harmonics, which is suitable for the production of high-order frequency multipliers. The cathodes of the two Schottky contacts are connected by the buffer layer without ohmic contact.