Heterojunction Photodiode Structure for Low-Intensity Light Burst Detection
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Solution Overview
Problem
Existing semiconductor photodiodes face challenges in detecting short, high-frequency, low-intensity light bursts due to high power consumption and complexity, and struggle with background noise rejection, especially in the near-infrared range, where silicon is inefficient.
Innovation Solution
A photodetecting component featuring a comparator circuit that electronically suppresses background noise and uses a silicon photomultiplier instead of a linear photodiode, along with a calibration circuit to adjust sensitivity, reducing the need for a power-hungry transimpedance amplifier and optical filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard linear photodetectors with transimpedance amplifier and analog-to-digital converter are used to detect short high-frequency low-intensity light bursts, then detection capability is achieved, but device complexity and power consumption increase substantially
Solution Approach 1:
The patent extracts and removes the complex transimpedance amplifier and analog-to-digital converter blocks from the detection system. Instead, it uses a simplified photodetector circuit that directly converts light signals to digital signals through a comparator and counter, eliminating unnecessary electronic components while maintaining detection capability for short high-frequency low-intensity light bursts
Solution Approach 2:
The patent replaces the traditional analog signal processing mechanism (transimpedance amplifier + ADC) with a direct digital detection mechanism using a photodetector coupled with a comparator and counter. This substitution eliminates complex analog electronics and reduces device complexity while preserving measurement precision
2Measurement precision
If optical filter is added to filter out background light and improve signal-to-noise ratio, then noise reduction is achieved, but device complexity and cost increase substantially
Solution Approach 1:
The patent removes the optical filter component from the system and replaces it with an electronic background light suppression mechanism. The photodetector circuit electronically identifies and suppresses background light signals through threshold comparison and selective counting, achieving noise reduction without adding optical filtering hardware
Solution Approach 2:
The patent substitutes the optical filtering mechanism (physical optical filter) with an electronic signal processing mechanism. The comparator circuit electronically distinguishes between background light and signal light based on intensity thresholds, replacing the need for physical optical filters and reducing device complexity
3Measurement precision
If highly selective optical filter is added to reduce background light noise, then signal-to-noise ratio improves, but manufacturing cost increases substantially
Solution Approach 1:
The patent extracts and eliminates the expensive highly selective optical filter from the system design. Instead, it uses a cost-effective electronic suppression approach where the photodetector circuit with comparator and counter electronically filters background light, achieving the same noise reduction function at lower manufacturing cost
Solution Approach 2:
The patent replaces expensive highly selective optical filters with inexpensive electronic components (photodetector, comparator, counter). These electronic components are cheaper to manufacture and integrate, reducing overall system cost while maintaining the ability to suppress background light noise
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 solution enhances signal-to-noise ratio, reduces power consumption, and simplifies the design while maintaining high measurement accuracy, making it suitable for applications like eye tracking in virtual and augmented reality.
Implementation Method 1
a semiconductor light absorption layer... the light absorption layer defines the active surface area for light entry into the photodiode
Implementation Method 2
a bulk structure made of a single semiconductor material such as silicon, the bulk structure comprising a p-type layer and an n-type layer, which together form the p-n junction of the photodiode
Data Source
AI summary
A semiconductor photodiode (600) comprises a top side (602) with an active surface area (604) for light entry, a bottom side (606), a bulk structure (610) made of a single semiconductor material, the bulk structure comprising a p-type layer (612a) and an n-type layer (612b), which together form the p-n junction (612) of the photodiode, wherein one of the two layers of the p-n junction is an upper p-n junction layer (612a) and the other one is a lower p-n junction layer (612b), wherein the upper p-n junction layer (612a) is located proximate to the active surface area (604), and a semiconductor light absorption layer (614), wherein the light absorption layer (612a), (614) defines the active surface area (604) and is arranged on top of the bulk structure (610), above the upper p-n junction layer (612a), and the semiconductor material of the light absorption layer (614) is different from the semiconductor material of the bulk structure (610), the light absorption layer (614) and the upper p-n junction layer (612a) thus forming a heterojunction, and the photodiode (600) further comprises a precursor layer (620) arranged between the bulk structure (610) and the light absorption layer (614), the light absorption layer (614) being grown on the precursor layer.