Electrically Modulated IR Photodiode for Low-Power CMOS Integration
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Solution Overview
Problem
Current electrically modulated photodiodes, such as CAPD, require continuous current flow to change spectral sensitivity, leading to high power consumption, which is a disadvantage for integrating multiple detector elements in a small space.
Innovation Solution
An electrically modulatable photodiode design featuring a substrate with two p-n junctions, where one junction is used for spectral detection and the other for modulation, allowing for switching between floating and voltage-applied states to control spectral sensitivity without continuous current flow, minimizing current losses and enabling efficient modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If continuous current flow is applied to modulate spectral sensitivity (CAPD method), then spectral sensitivity modulation is achieved, but power consumption increases significantly
Solution Approach 1:
The photodiode is segmented into two separate p-n junctions: one dedicated to detection and the other to modulation. This segmentation allows the modulation function to be performed by a separate structure that can be switched on and off, eliminating the need for continuous current flow through the detection junction and thereby reducing power consumption while maintaining spectral sensitivity modulation capability.
Solution Approach 2:
The modulation p-n junction is switched periodically between active and inactive states rather than maintaining continuous current flow. This periodic switching approach achieves the necessary spectral sensitivity modulation while minimizing average power consumption, as the modulation junction only draws significant current during switching transitions rather than continuously.
2Use of energy by moving object
If two p-n junctions are integrated in the substrate, then spectral sensitivity modulation without continuous current is achieved, but device structure becomes more complex
Solution Approach 1:
Two p-n junctions are integrated within a single semiconductor substrate, merging the detection and modulation functions into one unified device structure. This integration approach, while increasing structural complexity compared to a single junction, allows both functions to operate simultaneously without requiring separate discrete components, and enables the system to achieve low-power operation through the switching capability of the modulation junction.
Solution Approach 2:
The semiconductor substrate serves multiple functions by hosting both the detection p-n junction and the modulation p-n junction. This multi-functional design allows the single substrate to perform both spectral detection and spectral sensitivity modulation, reducing the need for separate components and potentially simplifying the overall system architecture despite the increased complexity within the substrate itself.
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 design achieves high modulation contrast and spectral sensitivity while reducing power consumption, allowing for efficient operation of multiple detector elements in a compact space with minimal current losses.
Implementation Method 1
charge carriers which have been generated by impinging radiomagnetic waves in the substrate
Implementation Method 2
charge carriers which can move towards the first further contact under the effect of the electric field of the p-n junction
Implementation Method 3
a steady-state electric field is generated in the substrate by a doping gradient
Data Source
AI summary
Electrically modulatable photodiode, comprising a substrate having a first and a second p-n junction, a common contact for jointly contacting the p or n dopings of the two p-n junctions, and two further contacts for separately contacting the other doping of the p and n dopings of the two p-n junctions, and a circuit, wherein the circuit is designed to measure a current flow caused by charge carriers which have been generated by impinging radiomagnetic waves in the substrate and which have reached the first further contact, and to switch the second further contact at different times to at least one first and one second switching state, wherein in the first switching state the second further contact is switched to the floating state and in the second switching state a potential is applied, and wherein a blocking voltage applied between the common contact and the first further contact is constant.