Avalanche Photodiode Digital-Alloy Region for Lidar Sensitivity
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Solution Overview
Problem
Current lidar systems face challenges in efficiently detecting and measuring distances to remote targets due to low return signal power and limited range, which affects their accuracy and operational range.
Innovation Solution
The lidar system incorporates a laser source emitting light in the infrared, visible, or ultraviolet spectrum, with a scanner and receiver configuration that includes an avalanche photodiode to detect scattered light, allowing for precise distance measurement based on time-of-flight analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photodetectors are used in lidar systems, then the system structure remains simple, but the detection sensitivity is insufficient and the operational range is limited
Solution Approach 1:
The patent changes the operating parameters of the photodetector by applying high reverse bias voltage to enter the avalanche multiplication regime, transforming the detection mechanism from linear to nonlinear with internal gain. This parameter change enables single-photon detection capability while maintaining a relatively simple device structure.
Solution Approach 2:
The patent employs composite semiconductor structures including InGaAs and InAlAs layers to create the avalanche photodiode. These composite materials provide both high quantum efficiency for infrared detection and sufficient breakdown voltage for avalanche multiplication, achieving enhanced sensitivity without excessive complexity.
2Length of stationary object
If the lidar system operates at extended ranges, then the measurement range increases, but the return signal power becomes too weak for accurate detection
Solution Approach 1:
The patent utilizes the avalanche breakdown phenomenon - a transient, high-field effect that occurs only during specific voltage conditions - to generate internal gain. This allows the system to detect extremely weak return signals from long-range targets by converting rare photon events into measurable electrical signals through controlled breakdown.
Solution Approach 2:
By changing the bias voltage parameter to exceed the breakdown voltage, the system transforms the photodetector's response characteristics from linear to avalanche multiplication mode, providing the necessary signal amplification to detect faint returns from extended ranges.
3Measurement precision
If high sensitivity detection is implemented, then the detection precision improves, but the noise level increases
Solution Approach 1:
The patent creates localized high-field regions within the InAlAs multiplication layer where avalanche multiplication occurs. This spatial confinement of the gain mechanism allows selective amplification of signal photons while maintaining control over noise generation through precise voltage biasing and structural design.
Solution Approach 2:
The patent replaces external signal amplification mechanisms with an internal electronic multiplication process driven by avalanche breakdown. This substitution eliminates the need for separate amplifier stages that would add electronic noise, achieving signal enhancement directly at the detection point.
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 enhances the system's ability to accurately measure distances over a wider range with improved sensitivity, enabling more precise scanning and data collection.
Implementation Method 1
an avalanche photodiode to detect scattered light
Implementation Method 2
low-noise avalanche photodiode
Implementation Method 3
a laser which emits light having a particular operating wavelength
Implementation Method 4
the lidar system may determine the distance to the target based on the time of flight for a pulse of light emitted by the light source to travel to the target and back to the lidar system
Data Source
AI summary
In one embodiment, a lidar system includes a light source configured to emit an optical signal and a receiver configured to detect an input optical signal that includes a portion of the emitted optical signal scattered by a target located a distance from the lidar system. The receiver includes an avalanche photodiode (APD) configured to receive the input optical signal and produce a photocurrent signal corresponding to the input optical signal. The APD includes a multiplication region that includes a digital-alloy region that includes two or more semiconductor alloy materials arranged in successive layers. The digital-alloy region is configured to produce at least a portion of the photocurrent signal by impact ionization. The receiver is configured to determine, based on the photocurrent signal produced by the APD, a round-trip time for the portion of the emitted optical signal to travel to the target and back to the lidar system.