Semiconductor Light Receiving Element DBR Layer Design
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Solution Overview
Problem
Existing semiconductor light receiving elements with distributed Bragg reflector (DBR) layers face challenges in achieving high light-receiving sensitivity in the 1.3 μm band due to difficulties in controlling the thickness and material composition of DBR layers, leading to poor reproducibility and low reflectance, which limits their sensitivity.
Innovation Solution
A semiconductor light receiving element is designed with a DBR layer composed of alternately laminated InP and InGaAsP layers, where the band-gap wavelength of InGaAsP layers is between 1.30 μm and 1.55 μm, and the sum of the optical layer thicknesses of these layers is approximately half the wavelength of the incident light, optimizing reflectance and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of pairs of InGaAsP layers and InP layers in the DBR layer is increased to 17 or more to achieve 70% or more reflectance, then the reflectance is improved, but the uniform control of thickness and material composition on the wafer surface becomes difficult and reproducibility deteriorates
Solution Approach 1:
The patent changes the material composition parameters of the DBR layer by using InGaAsP layers with a band-gap wavelength of 1.30 μm to 1.55 μm (corresponding to specific As-P composition ratios) instead of conventional materials. This parameter change enables achieving high reflectance with fewer layer pairs, thereby improving manufacturing precision and reproducibility while maintaining reliable optical performance
Solution Approach 2:
The patent employs composite material structure with specific InGaAsP and InP layer combinations where the InGaAsP layers have optimized composition ratios (As-P ratio of 9:1 or 8:2) to achieve the desired band-gap wavelengths. This composite approach allows precise control of optical properties while reducing the number of required layer pairs, resolving the contradiction between reflectance and manufacturing precision
2Reliability
If the total layer thickness of DBR layers is increased to 3.3 μm or more to achieve 70% or more reflectance, then the reflectance is improved, but the uniform control of thickness on the wafer surface becomes difficult and reproducibility deteriorates
Solution Approach 1:
The patent optimizes the thickness parameters of individual DBR layers by designing each InGaAsP layer and InP layer with specific thickness values that satisfy the quarter-wave condition for the target wavelength. This parameter optimization reduces the total DBR layer thickness while achieving high reflectance, thereby improving thickness uniformity control and reproducibility on the wafer surface
3Reliability
If a material composition with the largest difference in refractive indices is selected for the DBR layer, then the reflectance is elevated sharply with up to about 10 pairs, but the reflectance saturates at around 15 pairs and 40% or higher reflectance cannot be obtained
Solution Approach 1:
The patent changes the optical parameters of the DBR layer materials by selecting InGaAsP layers with band-gap wavelengths of 1.30 μm to 1.55 μm, which provides optimal refractive index contrast with InP layers. This parameter change enables the reflectance to continue increasing beyond 15 layer pairs, achieving over 40% reflectance while maintaining a reasonable number of layer pairs and avoiding saturation
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 enhances light-receiving sensitivity to 0.9 A/W or higher by achieving high reflectance and improving the uniform control and reproducibility of the DBR layer, even with a small number of pairs, thereby increasing the element's efficiency in the 1.3 μm band.
Implementation Method 1
a distributed Bragg reflector layer of a first conductivity type, an optical absorption layer, and a semiconductor layer of a second conductivity type which are sequentially laminated on the semiconductor substrate, wherein the distributed Bragg reflector layer includes first semiconductor layers and second semiconductor layers which are alternately laminated
Implementation Method 2
the sum of an optical layer thickness of one of the first semiconductor layers and an optical layer thickness of one of the second semiconductor layers is approximately half of the wavelength of the incident light
Implementation Method 3
an optical absorption layer... Light that has not been absorbed in and has passed through the optical absorption layer is reflected by the DBR layer and absorbed again in the optical absorption layer
Data Source
AI summary
A semiconductor light detecting element includes: a semiconductor substrate; and a distributed Bragg reflector layer of a first conductivity type, an optical absorption layer, and a semiconductor layer of a second conductivity type, sequentially laminated on the semiconductor substrate. The distributed Bragg reflector layer includes first and second alternately laminated semiconductor layers with different band-gap wavelengths, sandwiching the wavelength of detected incident light. The sum of thicknesses a first and a second semiconductor layer is approximately one-half the wavelength of the incident light detected.