Silicon Sensor Element Structure for Long-Wavelength Detection
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Solution Overview
Problem
Conventional silicon-based light-receiving elements are unable to detect light with wavelengths shorter than the band gap of silicon, and when made sensitive to such wavelengths, they emit light, causing noise and reducing their effectiveness.
Innovation Solution
A sensor element configuration with a p-n junction between silicon semiconductor portions with specific impurities, and a manufacturing method involving forward current and light irradiation to diffuse impurities, reducing self-emission and enhancing sensitivity to longer wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If silicon-based light-receiving elements are made sensitive to wavelengths longer than the band gap, then sensitivity to specific wavelengths is improved, but light emission of the element itself increases causing noise
Solution Approach 1:
The patent applies local quality by creating a multi-layered semiconductor structure where different regions have different impurity concentrations and types. Specifically, a first semiconductor layer has a first impurity concentration, a second semiconductor layer has a second impurity concentration, and a third semiconductor layer has a third impurity concentration, with the relationship: first impurity concentration < second impurity concentration < third impurity concentration. This gradient structure allows the device to achieve wavelength sensitivity beyond the silicon band gap while suppressing self-emission noise through localized impurity distribution optimization.
Solution Approach 2:
The patent employs parameter changes by systematically varying impurity concentration across different semiconductor layers. The key parameter relationship is: first impurity concentration < second impurity concentration < third impurity concentration, where each layer's impurity concentration is optimized to achieve the desired wavelength sensitivity while controlling light emission. This parameter gradient approach enables the device to detect wavelengths longer than the silicon band gap without excessive self-emission noise.
2Ease of operation
If conventional silicon light-receiving elements operate at room temperature, then ease of operation is improved, but sensitivity to wavelengths longer than the band gap cannot be achieved
Solution Approach 1:
The patent achieves room temperature operation with extended wavelength sensitivity by changing the impurity concentration parameter across semiconductor layers. The specific parameter relationship (first impurity concentration < second impurity concentration < third impurity concentration) creates a gradient structure that enables detection of wavelengths longer than the silicon band gap at room temperature, eliminating the need for cooling while maintaining sensitivity.
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 sensor element achieves reduced self-emission, increased sensitivity, and stable operation across a wide temperature range, with sensitivity to wavelengths beyond the silicon band gap without cooling.
Implementation Method 1
irradiating the layered body with light having a wavelength longer than a wavelength corresponding to a band gap of silicon
Implementation Method 2
diffusing the n-type impurity by irradiating the layered body with light having a wavelength longer than a wavelength corresponding to a band gap of silicon while applying a forward current to the layered body
Data Source
AI summary
A sensor element includes a first silicon semiconductor portion, a second silicon semiconductor portion, a third silicon semiconductor portion, and a p-n junction. The first silicon semiconductor portion includes a first p-type impurity. The second silicon semiconductor portion is arranged on the first silicon semiconductor portion and includes a second p-type impurity. The third silicon semiconductor portion is arranged on the second silicon semiconductor portion and includes an n-type impurity. The p-n junction is defined between the second silicon semiconductor portion and the third silicon semiconductor portion. The sensor element has light-receiving sensitivity to light having a wavelength longer than a wavelength corresponding to a band gap of silicon.