Infrared Semiconductor Device with Graded InGaAs Filter
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Solution Overview
Problem
Existing infrared detecting semiconductor devices face challenges in optimizing optical response characteristics across the 1.3 to 2.5 micrometer wavelength range, leading to variations in sensitivity that limit their application.
Innovation Solution
An infrared detecting semiconductor device is designed with a supporting base, a first conductivity-type semiconductor layer, a second conductivity-type semiconductor layer, and an optical filtering film of n-type InGaAs with varying dopant concentrations, which compensates for the optical response characteristics of the light absorbing layer by adjusting light absorption and transmission properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional optical filtering film with uniform dopant concentration is used, then the device structure is simple, but the optical response characteristics cannot be optimized across the 1.3 to 2.5 micrometer wavelength range
Solution Approach 1:
The optical filtering film employs a non-uniform dopant concentration distribution where the n-type dopant concentration varies through the film thickness. Specifically, the dopant concentration is higher near the light absorbing layer and decreases toward the outer surface, creating localized optical properties that compensate for the wavelength-dependent response variations in the 1.3 to 2.5 micrometer range
Solution Approach 2:
The invention changes the dopant concentration parameter spatially within the optical filtering film. By controlling the n-type dopant concentration to decrease from the interface with the light absorbing layer toward the outer surface, the optical absorption characteristics are adjusted to achieve more uniform sensitivity across different infrared wavelengths
2Reliability
If the optical filtering film absorbs more light to improve sensitivity, then the detection capability increases, but the light transmission to the light absorbing layer decreases
Solution Approach 1:
The optical filtering film creates different optical density zones through spatial variation of dopant concentration. The region near the light absorbing layer has higher dopant concentration for strong light absorption and sensitivity enhancement, while the outer regions have lower dopant concentration to allow sufficient light transmission to reach the active detection layer
Solution Approach 2:
The optical filtering film acts as an intermediary layer between the incident light and the light absorbing layer. By optimizing its dopant concentration profile, it mediates the light transmission process to achieve both adequate light delivery to the detector and sufficient optical absorption for sensitivity compensation across the infrared spectrum
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 device achieves improved optical response characteristics across the sensitive wavelength range, enabling enhanced sensitivity and application flexibility by independently managing light absorption and electrical performance through the n-type dopant profile of the optical filtering film.
Implementation Method 1
InGaAs having an n-type dopant concentration larger than 8×10^17 cm^-3 has a Moss-Burstein effect, and thus has an optical transition forbidden band larger than an inherent band gap of InGaAs and has higher optical transmittance in a wavelength band of light which undoped InGaAs or lightly-doped InGaAs absorbs
Data Source
AI summary
An infrared detecting semiconductor device comprises: an optical absorbing layer of type-II disposed between first conductivity-type and second conductivity-type semiconductor layers; and an optical filtering film of n-type InGaAs having an n-type dopant concentration larger than 8×1017 cm−3. The optical filtering film includes first to third semiconductor regions, which are sequentially arranged in a direction of a first axis on the optical filtering film. The first semiconductor region has an n-type dopant concentration of 2.0×1019 cm−3 or more. The third semiconductor region has a n-type concentration of 3.0×1018 cm−3 or less. The second semiconductor region has an n-type dopant profile monotonically changing from a first dopant concentration at a boundary between the first and second semiconductor regions to a second dopant concentration at a boundary between the second and third semiconductor regions. The first dopant concentration is greater than the second dopant concentration.