Stacked Silicon and Quantum Dot Photodiodes for Multispectral Sensing

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Solution Overview

Problem

Existing photodiodes are not sensitive to both visible and infrared wavelengths, particularly at near-infrared and short-wave infrared wavelengths, and existing solutions are costly or inefficient.

Innovation Solution

A device comprising a stack of a silicon photodiode and a quantum dot-based photodiode, with filters to separate and direct visible and infrared wavelengths to their respective photodiodes, allowing for high-performance multispectral detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single silicon photodiode is used, then the device is simple and low-cost, but it cannot detect infrared wavelengths effectively

Engineering Contradiction:

Improveinfrared detection capabilityVSAvoidphotodiode structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines a silicon photodiode and a quantum dot photodiode into a single integrated device. The silicon photodiode detects visible light while the quantum dot photodiode detects infrared wavelengths, merging two detection capabilities into one unified structure that overcomes the limitations of single-material photodiodes

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention uses composite materials by stacking two different photodiode technologies (silicon and quantum dots) with complementary spectral responses. This composite structure enables simultaneous detection of visible and infrared wavelengths, leveraging the strengths of each material system

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If multiple photodiodes are stacked to detect both visible and infrared wavelengths, then spectral detection capability is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvemultispectral detection capabilityVSAvoidstack fabrication process

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The device is segmented into distinct functional layers: a silicon photodiode layer for visible light detection and a quantum dot photodiode layer for infrared detection. This segmentation allows each layer to be optimized for its specific wavelength range while maintaining manufacturability through modular fabrication processes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An optical filter is introduced as an intermediary element between the two photodiodes. This filter selectively transmits infrared wavelengths to the quantum dot photodiode while blocking visible wavelengths, enabling clean spectral separation and simplifying the manufacturing process by preventing cross-interference between the two detection channels

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If filters are added to separate wavelengths, then detection precision is improved, but device complexity increases

Engineering Contradiction:

Improvewavelength discrimination accuracyVSAvoidfilter integration structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The optical filter serves as an intermediary that automatically performs wavelength discrimination. By placing the filter in the optical path between the light source and the quantum dot photodiode, it passively separates infrared from visible wavelengths without requiring complex active control mechanisms, thereby improving measurement precision while adding minimal structural complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enables high-performance detection of both visible and infrared light, including short-wave infrared, at reduced costs, facilitating applications such as multispectral ambient light detection and proximity sensing.

Implementation Method 1

A photodiode is a semiconductor component having the ability to capture a radiation in the optical field and to transform it into an electrical signal

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

a second photodiode based on quantum dots wherein the first silicon photodiode is arranged between a side of the stack configured to receive incident light and the second photodiode

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 3

the device comprises a first filter interposed between the first silicon photodiode and the second photodiode, said first filter configured to let through infrared wavelengths and reflect visible wavelengths

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Data Source

PatentUS20250393326A1Electronic device

Publication Date: 2025.12.25 STMICROELECTRONICS INT NV

AI summary

An imaging device includes a stack formed by a first silicon photodiode and a second photodiode based on quantum dots. The first silicon photodiode is arranged between a side of the stack configured to receive incident light and the second photodiode. The incident light includes infrared wavelengths and visible wavelengths. A filter positioned between the first silicon photodiode and the second photodiode reflects visible wavelengths back to the first silicon photodiode and passes infrared wavelengths through to the second photodiode.