Charge Modulation Element for High-Speed TOF Sensors
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Solution Overview
Problem
Existing optical time-of-flight (TOF) sensors face challenges in achieving high-speed operations due to large capacitance changes and inefficient power dissipation, primarily because they rely on slow carrier components and wide neutral regions in semiconductor substrates.
Innovation Solution
A charge-modulation element with a photoelectric-conversion layer, surface-buried and modulation regions of different conductivity types, and potential-control regions that control charge-transport routes to accumulate signal charges efficiently, reducing power dissipation and enabling high-speed TOF operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If majority-carrier currents are injected from injection contact regions into the p-type semiconductor substrate, then optical currents can be collected, but power dissipation increases
Solution Approach 1:
The invention extracts and eliminates the majority-carrier current injection mechanism from the photonic mixer structure. By removing the injection contact regions and stopping the injection of majority-carrier currents into the semiconductor substrate, the source of excessive power dissipation is eliminated while maintaining the optical current collection function through alternative charge generation mechanisms
Solution Approach 2:
The invention changes the operational parameters by transitioning from majority-carrier current injection to minority-carrier current utilization. This parameter change involves modifying the conductivity types and impurity concentrations of semiconductor regions to enable efficient charge generation and collection without the harmful majority-carrier injection process
2Speed
If a wide neutral region is used in the p-type semiconductor substrate, then charge collection area is increased, but operation speed decreases due to slow carrier diffusion
Solution Approach 1:
The invention substitutes the slow diffusion-based charge transport mechanism with a faster drift-based mechanism. By replacing reliance on carrier diffusion through wide neutral regions with electric field-driven charge drift in depleted regions, the operation speed is dramatically increased while maintaining effective charge collection
Solution Approach 2:
The invention changes the electrical parameters of the semiconductor substrate by creating depleted regions with appropriate electric fields. This involves modifying the impurity concentration distribution and applying bias voltages to transform the charge transport mechanism from diffusion-limited to field-driven, thereby increasing operation speed
3Productivity
If large capacitance change is involved in electric field control, then charge modulation capability is improved, but operation efficiency decreases
Solution Approach 1:
The invention changes the capacitance parameters by optimizing the geometry and doping profiles of the semiconductor regions. By carefully designing the depletion region dimensions and impurity concentrations, the capacitance change during operation is minimized while maintaining sufficient charge modulation capability for effective TOF detection
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 solution allows for high-speed TOF operations with low power dissipation by controlling charge-transport routes and accumulating signal charges effectively, enhancing the efficiency of the TOF architecture.
Implementation Method 1
a photoelectric-conversion layer of a first conductivity type... configured to implement a photodiode with the photoelectric-conversion layer
Data Source
AI summary
A charge-modulation element encompasses a p-type photoelectric-conversion layer, a n-type surface-buried region buried in an upper portion of the photoelectric-conversion layer configured to implement a photodiode with the photoelectric-conversion layer, a n-type modulation region buried in another part of the upper portion of the photoelectric-conversion layer configured to implement a part of the photodiode with the photoelectric-conversion layer, potential-control regions assigned in one of divided areas, n-type charge-accumulation regions configured to accumulate signal charges generated in the photodiode. Potentials in the modulation region and the surface-buried region are controlled by route-select signals applied to the potential-control regions so as to select one of the charge-transport routes, which transfers the signal charges toward one of the charge-accumulation regions.