Silicon Backward Diodes for Zero-Bias Millimeter-Wave Detection
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Solution Overview
Problem
Existing silicon-based millimeter-wave detectors and imagers face challenges with biasing circuits increasing complexity and noise, and Sb-based backward diodes are costly and incompatible with mainstream silicon read-out circuitry, limiting their suitability for imaging applications.
Innovation Solution
The development of silicon-based backward diodes with a p-n junction and a tunnel barrier or quantum well structure, which reduces forward tunneling current relative to backward tunneling current, and the use of SiGe layers or delta doping to enhance nonlinearity and compatibility with silicon substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If biased Schottky diodes are used for millimeter-wave detection, then detection functionality is achieved, but system complexity and noise increase due to biasing circuits
Solution Approach 1:
The patent extracts and eliminates the biasing circuit from the detection system by using zero-bias backward diodes. The backward diode structure inherently provides the necessary nonlinearity for detection without requiring external biasing, thus removing the source of complexity and noise while maintaining detection functionality.
Solution Approach 2:
The backward diode structure is designed to be self-sufficient for detection purposes. The asymmetric tunneling characteristics of the backward diode automatically provide the required nonlinearity for square-law detection without needing external biasing circuits, making the device self-service and eliminating additional components.
2Reliability
If Sb-based heterojunction backward diodes are used for zero-bias detection, then high sensitivity and mass production capability are achieved, but cost increases and compatibility with silicon read-out circuitry is lost
Solution Approach 1:
The patent uses homogeneous silicon material for the backward diode structure instead of heterojunction materials like Sb-based compounds. This homogeneity ensures compatibility with mainstream silicon fabrication processes and silicon read-out circuitry, while still achieving the desired detection performance through optimized silicon-based tunnel barrier structures.
Solution Approach 2:
The patent changes the material parameters by using silicon with carefully controlled doping concentrations and tunnel barrier thicknesses. By adjusting these parameters, the silicon-based backward diode achieves high detection sensitivity comparable to heterojunction devices while maintaining compatibility with silicon technology ecosystems.
3Reliability
If discrete Ge backward diodes or planar-doped barrier GaAs diodes are used for zero-bias detection, then high nonlinearity is achieved, but mass production and imaging array fabrication become difficult
Solution Approach 1:
The silicon-based backward diode structure is designed to be universal and compatible with existing silicon semiconductor manufacturing processes. This allows the same fabrication infrastructure used for silicon electronics to produce backward diodes for imaging arrays, achieving both high nonlinearity and mass production capability simultaneously.
Solution Approach 2:
The patent employs composite silicon structures with tailored doping profiles and tunnel barrier layers. By combining different silicon regions with specific properties (heavily doped contact regions, lightly doped tunnel regions), the device achieves high nonlinearity while remaining compatible with standard silicon processing techniques for mass production.
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 silicon-based backward diodes exhibit high nonlinearity, low junction resistance, and compatibility with silicon technology, making them suitable for zero-bias detector applications with improved sensitivity and mass production capabilities.
Implementation Method 1
The tunnel barrier causes the forward tunneling current to be substantially smaller than the backward tunneling current at comparable voltage levels
Implementation Method 2
a quantum well disposed at or near the silicon based p-n junction. The quantum well causes a ratio of forward current to backward current at comparable forward and reverse bias voltage levels to be substantially less than unity
Implementation Method 3
a Si-based pn junction disposed on the silicon substrate. The Si-based pn junction includes silicon and at least one SiGe layer that reduces a tunneling barrier height
Implementation Method 4
At least one delta doping is disposed on the silicon substrate in or near the pn junction, the at least one delta doping together with the Si-based pn junction defining an electrical junction having a backward diode current-voltage characteristic
Data Source
AI summary
A Si-based diode (10, 10′, 100) is formed by epitaxially depositing a Si-based diode structure on a silicon substrate. The Si-based diode structure includes a Si-based pn junction (16, 16′, 18, 18′, 30, 32, 160, 161) having a backward diode current-voltage characteristic in which the forward tunneling current is substantially smaller than the backward tunneling current at comparable voltage levels. In some embodiments, the Si-based pn junction includes at least one non-silicon or silicon alloy layer such as at least one SiGe layer (16, 16′, 160, 161). In some embodiments, at least one delta doping (30, 32) is disposed on the silicon substrate in or near the pn junction, that together with the Si-based pn junction define an electrical junction having the backward diode current-voltage characteristic. A large area detector array may include a plurality of such Si-based diodes (10, 10′, 100).