Kyoto Semiconductor Develops Broad Range Sensitivity Photodiode in the Industry’s Smallest Class

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In the 40 years since the company’s founding, Kyoto Semiconductor Co., Ltd., Tsuneo Takahashi, President and CEO, and headquartered in Fushimi Ward, Kyoto, has led the industry with optical solutions built from world-standard technologies and with Japanese quality and attention to production detail. 

They have announced the development of a Two-Wavelength Photodiode, the KP-2 Two-tone Photodiode KPMC29, in the industry’s smallest class and capable of being surface-mounted, with silicon and indium-gallium-arsenide photodiodes, with photosensitivity for a wide range of wavelengths, from 400 to 1,700 nm, arrayed along the same light axis.

This broadband sensitivity, together with a smaller package that is 1/8 the volume ratio of older Kyoto Semiconductor products, can be used in the healthcare field for applications that include medical biometric monitoring like pulse oximeters as well as wearable activity monitors. Because it is also possible to independently produce photocurrent signals from the silicon and indium-gallium-arsenide photodiodes, measuring the photocurrent ratio will allow for its use as a radiation thermometer that can measure temperatures without direct contact with hot object.

Development Background

Spectroscopic analysis technology, that allows for the identification of objects and their characteristics without needing direct contact with those objects, by reflecting light of those objects and measuring the degrees of transmission and reflection, is increasingly needed in a wide range of fields, including medicine, production, and security. Spectroscopic analysis relies on two factors for successful use in identifying a wide range of objects: a wider range of wavelengths, or colors, for the source wavelengths, and a wider range of sensitivity for those wavelengths with the photodiode end. There is also a need for smaller products, compared to existing corded-lead products, for use with medical equipment or wearable devices that can be worn directly on the human body.

Development was therefore undertaken to meet these product needs.

Product Characteristics

1. A wider range of wavelength sensitivity (400~1,700nm).
   To expand the wavelength range, we layered both silicon photodiodes, which are sensitive to shorter wavelengths, and indium-gallium-arsenide photodiodes, which are sensitive to longer wavelengths, along the same light axis.
2. A compact surface-mountable package in the industry’s smallest class.
   To successfully make this KP-2 two-tone PD smaller, the indium-gallium-arsenide photodiodes were laid down in pits arranged on the base for the silicon photodiodes, which ordinarily allows light to pass through. This allowed for the package height to be as low as possible. (Patents have been filed.)
   Compared to earlier products from Kyoto Semiconductor, the volume ratio has been reduced to 1/8.