Geiger-mode Avalanche Photodiode Array With Lateral Insulation
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Solution Overview
Problem
Geiger-mode avalanche photodiodes (GMAPs) are underutilized for infrared radiation detection due to high dark currents and signal-to-noise ratio reduction with increasing reverse biasing voltage, and they suffer from optical crosstalk and limited sensitive area, making them less effective for infrared detection applications.
Innovation Solution
An array of Geiger-mode avalanche photodiodes is designed with a semiconductor body structure that includes epitaxial layers and a lateral insulation region to reduce optical crosstalk and dark current, allowing for higher reverse biasing voltages and increased sensitive area while maintaining a high signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reverse biasing voltage is increased to improve detection efficiency and gain, then the sensitivity to infrared radiation is improved, but the dark current increases considerably and the signal-to-noise ratio is reduced
Solution Approach 1:
The invention divides the semiconductor body into multiple epitaxial layers with different doping levels and functions. The first epitaxial layer has higher doping level than the second, creating distinct regions for carrier generation and multiplication. This segmentation allows the device to operate at higher reverse biasing voltages while maintaining controlled dark current through the structured doping profile.
Solution Approach 2:
The invention applies different doping levels to different regions (first epitaxial layer has higher doping than second) and introduces a lateral insulation region with specific doping characteristics. This local differentiation of material properties enables the photodiode to achieve both high gain through avalanche multiplication and reduced dark current through optimized local carrier generation and collection.
2Power
If the reverse biasing voltage is increased to improve gain, then the avalanche multiplication gain is improved, but the signal-to-noise ratio is reduced
Solution Approach 1:
The segmented epitaxial structure with differentiated doping levels enables separation of the high-field avalanche region from lower-field collection regions. This allows operation at higher reverse biasing voltages for improved gain while the structured doping profile suppresses spurious carrier generation, thereby maintaining signal-to-noise ratio.
Solution Approach 2:
The invention optimizes the doping levels of the epitaxial layers and the reverse biasing voltage as key parameters. By carefully selecting the doping concentration in each layer and the operating voltage, the device achieves high avalanche multiplication gain while controlling dark current and maintaining favorable signal-to-noise ratio.
3Area of stationary object
If the sensitive area is increased to improve detection capability, then the detection capability is improved, but the dark current increases and the signal-to-noise ratio is reduced
Solution Approach 1:
The invention employs a segmented epitaxial structure with lateral insulation regions that electrically isolate different areas of the photodiode. This segmentation allows the sensitive area to be extended for improved detection capability while the lateral insulation prevents dark current generated in one region from affecting the entire device, thereby maintaining signal-to-noise ratio.
4Measurement precision
If higher reverse biasing voltage is used to improve detection efficiency, then the infrared radiation detection is improved, but optical crosstalk between adjacent photodiodes increases
Solution Approach 1:
The invention introduces lateral insulation regions that physically and electrically segment adjacent photodiodes. These insulation regions, formed with specific doping characteristics, block the propagation of secondary photons generated during avalanche multiplication in one photodiode from reaching adjacent photodiodes. This segmentation effectively reduces optical crosstalk even when operating at higher reverse biasing voltages that improve detection efficiency.
Solution Approach 2:
The lateral insulation region acts as an intermediary barrier between adjacent photodiodes. It absorbs or blocks secondary photons generated in one photodiode before they can trigger spurious avalanches in neighboring photodiodes, thereby reducing optical crosstalk while allowing the photodiodes to operate at higher bias voltages for improved detection efficiency.
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 enables improved detection efficiency and signal-to-noise ratio with reduced dark current, allowing for larger sensitive areas and higher gain without the limitations of traditional GMAPs, particularly effective in infrared radiation detection.
Implementation Method 1
generation of a single electron-hole pair, following upon absorption of a photon incident on the SPAD
Implementation Method 2
This ionization process in turn causes an avalanche multiplication of the carriers, with gains of around 10^6
Implementation Method 3
the photons generated by electroluminescence during avalanche multiplication processes triggered in surrounding SPADs
Implementation Method 4
The secondary photons may propagate and be subsequently absorbed in the junctions of SPADs different from the SPADs in which they have been generated
Data Source
AI summary
An array of Geiger-mode avalanche photodiodes is formed in a die and includes: an internal dielectric structure, arranged on the die; and an external dielectric region arranged on the internal dielectric structure. The external dielectric region is formed by an external material that absorbs radiation having a wavelength that falls in a stop-band with low wavelength and transmits radiation having a wavelength that falls in a pass-band with high wavelength, at least part of the pass-band including wavelengths in the infrared. The internal dielectric structure is formed by one or more internal materials that substantially transmit radiation having a wavelength that falls in the stop-band and in the pass-band and have refractive indices that fall in an interval having an amplitude of 0.4. In the stop-band and in the pass-band the external dielectric region has a refractive index with the real part that falls in the above interval.