GaAs Wafers in Temperature Measurement Applications
Gallium Arsenide (GaAs), as a III-V group direct bandgap compound semiconductor, has unique spectral response characteristics that make it an ideal medium for temperature sensing. The bandgap width of this material shows a significant correlation with temperature. When it is excited by photons, it selectively absorbs characteristic wavelength photons that match the current bandgap width. Based on this temperature dependent characteristic, a quantitative mapping relationship between absorption spectra and temperature changes can be established by precisely detecting the wavelength shift of characteristic absorption peaks, thereby achieving non-contact temperature sensing. This provides a physical basis for the design of fiber optic temperature sensing systems. PAM-XIAMEN can provide GaAs wafers for temperature measurement technology research. For more wafer details, please refer to:
https://www.powerwaywafer.com/gaas-wafers/gaas-wafer.html
1. Advantages of GaAs to Prepare Temperature Measuring Devices
The bandgap of GaAs is highly sensitive to temperature, and as the temperature increases, its bandgap width decreases linearly, resulting in a red shift in the wavelength of the absorption spectrum. This change is reflected in the shift of the cutoff wavelength in the reflection spectrum or absorption spectrum, and the temperature value can be accurately calculated by measuring this wavelength change. Meanwhile, the optical properties of GaAs, especially the dielectric function, are closely related to temperature (as shown in Fig. 1), and this correlation can be detected and analyzed through optical measurement techniques such as spectroscopic ellipsometry (SE). Due to the extreme sensitivity of SE technology to changes in material optical constants, utilizing the optical properties of GaAs can detect small temperature changes, thereby achieving high sensitivity and accuracy in temperature measurement. The absorption edge of GaAs changes significantly with temperature, and even slight temperature fluctuations can cause significant displacement of the absorption edge, further improving the stability and accuracy of the measurement.
Fig. 1 Real part variation of pseudo dielectric function of GaAs at high temperature
In addition, a research has shown that the height of the Schottky barrier formed when GaAs comes into contact with metal varies with temperature, resulting in changes in the current voltage characteristics of the Schottky diode. By measuring this change, the temperature value can be calculated. The use of GaAs in fiber optic temperature sensing can also leverage its advantages in resisting electromagnetic interference, making it particularly suitable for use in strong electromagnetic field environments.
2. Multi Channel Fiber Optic Temperature Sensing System Based on GaAs Absorption
Yuming Dong et al. proposed an innovative low-cost multi-channel fiber optic temperature sensing system based on GaAs absorption, which effectively overcomes the technical bottleneck of traditional systems by integrating fiber optic multiplexing modules and time-division multiplexing technology. The fiber temperature sensing system operates based on the temperature dependent bandgap width characteristics of GaAs material, which means that only photons with energy greater than the GaAs bandgap width can be absorbed when the light beam passes through the GaAs device; As the temperature increases, the bandgap width of GaAs decreases, causing the wavelength of the absorption spectrum to shift towards longer wavelengths. The system uses a spectral analysis unit to measure the spectrum of reflected light and identify the position of the absorption edge of GaAs devices. Based on the change in the wavelength of the absorption edge, the system can calculate the temperature at which the GaAs device is located.
The multi-channel system uses time-division multiplexing and fiber optic multiplexing technologies to light up different light sources within a preset time period and transmit the light beams to the corresponding GaAs devices. Finally, the light beams from different GaAs devices are merged and transmitted to the spectral analysis unit. The system measures the temperature of each GaAs device within a preset time period and outputs corresponding temperature information.
This solution has the advantages of low cost, high reliability, fast speed, and long lifespan. The experimental data shows that the temperature measurement system can achieve a temperature resolution of -/+1 ℃, a measurement frequency of 2Hz, and is suitable for the temperature range of 0 ℃ to 150 ℃.
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Reference：
Yao, H. , Snyder, P. G. , & Woollam, J. A. . (1991). Temperature dependence of optical properties of gaas. Journal of Applied Physics, 70(6), 3261-3267.