SPAD Light-Receiving Element With Regional Temperature Compensation
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Solution Overview
Problem
SPADs in vehicle-mounted dToF ranging sensors generate heat non-uniformly due to photon detection and CMOS circuit activity, leading to temperature gradients that cause variations in electrical characteristics and decrease photon detection efficiency.
Innovation Solution
A light-receiving element with a pixel region and readout circuit region, each having elongated shapes, where thermometers measure temperature differences between circuit regions and control circuits adjust voltages to maintain uniformity, ensuring consistent photon detection across the SPADs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SPADs operate in Geiger mode to detect single photons, then photon detection capability is improved, but heat generation becomes non-uniform causing temperature gradients
Solution Approach 1:
The readout circuit region is divided into multiple circuit regions (first circuit region, second circuit region, etc.), each equipped with its own thermometer and control circuit. This segmentation allows independent temperature monitoring and compensation for each region, addressing the non-uniform heat generation across the SPAD array.
Solution Approach 2:
Each circuit region has dedicated temperature sensing (thermometer) and control circuits that apply region-specific voltage adjustments. This local quality approach ensures that temperature compensation is tailored to the specific thermal conditions of each region, maintaining optimal breakdown voltage characteristics despite overall temperature gradients.
2Loss of energy
If temperature gradient exists in readout circuit region, then heat dissipation is improved, but electrical characteristics such as breakdown voltage vary
Solution Approach 1:
Thermometers in each circuit region provide real-time temperature feedback to the control circuits. The control circuits use this feedback to dynamically adjust the voltage applied to corresponding SPADs, compensating for temperature-induced variations in breakdown voltage and maintaining stable electrical characteristics.
Solution Approach 2:
The control circuits change the voltage parameter applied to each SPAD based on the temperature measured by the corresponding thermometer. This parameter adjustment compensates for temperature effects on breakdown voltage, ensuring consistent electrical characteristics across regions with different temperature conditions.
3Reliability
If multiple thermometers and control circuits are added to compensate for temperature gradients, then electrical characteristics stability is improved, but device complexity increases
Solution Approach 1:
The readout circuit region is divided into multiple circuit regions (first circuit region, second circuit region, etc.), each equipped with its own thermometer and control circuit. This segmentation allows independent temperature monitoring and compensation for each region, addressing the non-uniform heat generation across the SPAD array.
Solution Approach 2:
Each circuit region has dedicated temperature sensing (thermometer) and control circuits that apply region-specific voltage adjustments. This local quality approach ensures that temperature compensation is tailored to the specific thermal conditions of each region, maintaining optimal breakdown voltage characteristics despite overall temperature gradients.
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 effectively suppresses variations in electrical characteristics and enhances photon detection efficiency by compensating for temperature gradients, maintaining consistent performance in varying temperature conditions.
Implementation Method 1
a first thermometer provided corresponding to a first circuit region of the readout circuit region; a second thermometer provided corresponding to a second circuit region of the readout circuit region
Implementation Method 2
a first control circuit that applies a first voltage corresponding to a temperature of the first circuit region measured by the first thermometer to the photodiode corresponding to the readout circuit in the first circuit region
Implementation Method 3
The SPAD is a light-receiving element that operates an avalanche photodiode (APD) in Geiger mode to enable detection of a single photon. When a single photon is incident while a reverse bias voltage higher than a breakdown voltage is applied, carriers undergo avalanche multiplication to generate a large current.
Data Source
AI summary
[Problem] Provided is a light-receiving element capable of suppressing variations in electrical characteristics even when there is a temperature gradient.[Solution] A light receiving element of the present disclosure includes: a pixel region in which a plurality of photodiodes is arranged; a readout circuit region including a plurality of readout circuits provided corresponding to the plurality of photodiodes, respectively; a first thermometer provided corresponding to a first circuit region of the readout circuit region; a second thermometer provided corresponding to a second circuit region of the readout circuit region; a first control circuit that applies a first voltage corresponding to a temperature of the first circuit region measured by the first thermometer to the photodiode corresponding to the readout circuit in the first circuit region; and a second control circuit that applies a second voltage corresponding to a temperature of the second circuit region measured by the second thermometer to the photodiode corresponding to the readout circuit in the second circuit region.