Semiconductor Light Detector Multilayer Reflection Wavelength Stability

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Solution Overview

Problem

Semiconductor light receiving elements exhibit low wavelength stability due to interference from multiple resonance modes, leading to significant changes in quantum efficiency with small variations in incident light wavelength.

Innovation Solution

A semiconductor light receiving element design featuring a semiconductor substrate with a multilayer reflective layer, an absorptive layer with a smaller band gap, and a phase adjusting layer with a larger band gap, where the multilayer reflective layer directly contacts the absorptive layer without intervening layers, reducing composite resonance modes and enhancing wavelength stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple resonance modes are present in the light receiving element structure, then light absorption efficiency is improved, but wavelength stability deteriorates due to interference between modes

Engineering Contradiction:

Improvelight absorption efficiencyVSAvoidwavelength stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent removes the phase adjusting layer that was causing harmful resonance mode interference. By extracting this specific layer from the structure, the harmful composite resonance modes are eliminated while maintaining the beneficial resonance modes for light absorption, thus resolving the contradiction between absorption efficiency and wavelength stability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent utilizes the resonance phenomenon that was causing wavelength instability and converts it into a beneficial effect. By carefully designing the cavity structure and reflective layers, the resonance is harnessed to enhance light absorption efficiency while the harmful interference modes are suppressed, turning a previously harmful effect into a beneficial one

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Device complexity

If the absorptive layer is thinned to reduce device complexity, then manufacturing precision is improved, but light absorption capability worsens

Engineering Contradiction:

Improvelayer structure complexityVSAvoidlight absorption capability

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent employs optical resonance (analogous to mechanical vibration) to enhance light absorption in the thinned absorptive layer. By creating resonant modes that trap and circulate light within the absorptive layer, the absorption capability is significantly enhanced despite the reduced thickness, allowing thin layers to maintain high absorption efficiency

Inventive Principle:

Principle #18Mechanical vibration

Solution Approach 2:

The patent uses periodic reflection of light between the reflective layers to create resonant standing waves within the absorptive layer. This periodic action of light bouncing back and forth increases the effective interaction time between light and the absorptive material, compensating for the reduced layer thickness and maintaining high absorption capability

Inventive Principle:

Principle #19Periodic action

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 design improves wavelength stability by minimizing fluctuations in quantum efficiency, maintaining high efficiency even with thin absorptive layers and reducing heat confinement, thereby stabilizing current output across varying wavelengths.

Implementation Method 1

The n-type multilayer reflective layer 102 and the p-type multilayer reflective layer 106 are layers formed by laminating semiconductor layers having different refractive indices, for example, InP and InGaAsP, and have a function to reflect or transmit light.

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

Light incident from the upper side of the drawing is absorbed in the absorptive layer 104 while reciprocating (resonating) between the n-type multilayer reflective layer 102 and the p-type multilayer reflective layer 106. Pairs of electrons and holes are generated from the absorbed light

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 3

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS7893460B2Semiconductor light detecting element including first and second multilayer light reflective structures sandwiching and contacting a light absorptive layer

Publication Date: 2011.02.22 MITSUBISHI ELECTRIC CORP

AI summary

A semiconductor light detecting element comprises: a semiconductor substrate having a first major surface and a second major surface opposite each other; a first reflective layer, an absorptive layer, a phase adjusting layer, and a second reflective layer sequentially disposed, from the semiconductor substrate, on the first major surface of the semiconductor substrate; and an anti-reflection film on the second major surface of the semiconductor substrate. The first reflective layer is a multilayer reflective layer including laminated semiconductor layers having different refractive indices; the absorptive layer has a band gap energy smaller than band gap energy of the semiconductor substrate; the phase adjusting layer has a band gap energy larger than the band gap energy of the absorptive layer; and the first reflective layer contacts the absorptive layer, without intervention of other layers.