Optical Sensor Structure for Photo-Carrier Gain With Low Dark Current
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Solution Overview
Problem
Existing optical sensors face challenges in efficiently amplifying photo-carriers while minimizing dark current and improving sensitivity, particularly in applications requiring high precision and low noise.
Innovation Solution
The optical sensing apparatus incorporates a substrate with a buried-dopant region, an amplification region, and a buffer layer, along with a cladding layer and conductive regions, to enhance photo-carrier collection and amplification, while the interface-dopant and buried-dopant regions are strategically doped to control electric fields and prevent premature breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the absorption region and buried-dopant region are placed close together to reduce device complexity, then the device structure is simplified, but premature breakdown occurs and sensitivity decreases
Solution Approach 1:
An intrinsic buffer layer is introduced between the absorption region and the buried-dopant region. This buffer layer acts as an intermediary that prevents direct interaction between the two regions, thereby avoiding premature breakdown while maintaining a relatively compact device structure. The buffer layer mediates the electric field distribution and prevents carrier multiplication in the absorption region.
2Object-generated harmful factors
If the buffer layer thickness is increased to reduce dark current, then dark current is reduced, but detection distance is limited
Solution Approach 1:
The buffer layer thickness is optimized to a specific range (50-200 nm) to achieve the right balance between reducing dark current and maintaining detection distance. This parameter optimization ensures that the buffer layer is thick enough to suppress dark current through reduced tunneling but thin enough to allow sufficient photo-carrier collection and maintain sensitivity for longer detection distances.
3Productivity
If the doping concentration in the buried-dopant region is increased to improve photo-carrier collection, then photo-carrier collection is enhanced, but breakdown voltage is reduced and dark current increases
Solution Approach 1:
The intrinsic buffer layer serves as a mediator that allows the buried-dopant region to maintain high doping concentration for effective photo-carrier collection while preventing the high electric field from extending into the absorption region. This mediation preserves the breakdown voltage and suppresses dark current generation.
Solution Approach 2:
The buffer layer creates a local quality transition zone with distinct electrical properties between the absorption region and buried-dopant region. This local differentiation allows high doping concentration in the buried-dopant region without compromising the overall device breakdown characteristics.
4Reliability
If the amplification region is designed to provide high gain to improve sensitivity, then sensitivity is enhanced, but dark current is also amplified
Solution Approach 1:
The buffer layer acts as a mediator that prevents the high electric field required for avalanche multiplication from extending into the absorption region where dark current is generated. This allows the amplification region to provide high gain for signal photo-carriers while suppressing dark current amplification.
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 improves the sensitivity and quantum efficiency of the optical sensing apparatus by effectively amplifying photo-carriers and reducing dark current, leading to enhanced performance in applications such as proximity sensing and time-of-flight ranging.
Implementation Method 1
an absorption region including a second material different from the first material, the absorption region configured to receive an optical signal and generate photo-carriers in response to receiving the optical signal
Implementation Method 2
an amplification region formed in the substrate configured to collect at least a portion of the photo-carriers from the absorption region and to amplify the portion of the photo-carriers
Data Source
AI summary
An optical sensing apparatus including: a substrate including a first material; an absorption region including a second material different from the first material; an amplification region formed in the substrate and configured to collect at least a portion of the photo-carriers from the absorption region and to amplify the portion of the photo-carriers; an interface-dopant region formed in the substrate between the absorption region and the amplification region; a buffer layer formed between the absorption region and the interface-dopant region; one or more field-control regions formed between the absorption region and the interface-dopant region and at least partially surrounding the buffer layer; and a buried-dopant region formed in the substrate and separated from the absorption region, where the buried-dopant region is configured to collect at least a portion of the amplified portion of the photo-carriers from the amplification region.