Abstract
We report the evaluation of a molecular-beam epitaxy grown two-color photodetector for radiation thermometry. This two-color photodetector consists of two p+in+ diodes, an In0.53Ga0.25Al0.22As (hereafter InGaAlAs) p+in+ diode, which has a cutoff wavelength of 1180 nm, and an In0.53Ga0.47As (hereafter InGaAs) p+in+ diode with a cutoff wavelength of 1700 nm. Our simple monolithic integrated two-color photodetector achieved comparable output signal and signal-to-noise (SNR) ratio to that of a commercial two-color Si-InGaAs photodetector. The InGaAlAs and InGaAs diodes detect blackbody temperature as low as 275°C and 125°C, respectively, with an SNR above 10. The temperature errors extracted from our data are 4°C at 275°C for the InGaAlAs diode and 2.3°C at 125°C for the InGaAs diode. As a ratio thermometer, our two-color photodetector achieves a temperature error of 12.8°C at 275°C, but this improves with temperature to 0.1°C at 450°C. These results demonstrated the potential of InGaAlAs-InGaAs two-color photodetector for the development of high performance two-color array detectors for radiation thermometry and thermal imaging of hot objects.
Highlights
RADIATION THERMOMETERS are widely used in non-contact temperature measurement systems where the target is inaccessible, for example due to the extremely high temperatures in a blast furnace or to prevent contamination in semiconductor wafer growth [1]-[3]
We report the first evaluation of an InGaAlAs-InGaAs two-color photodetector for radiation thermometry
Bulk current density of 10-6 A/cm2 was obtained in the InGaAlAs, while the inconsistency of the current density in the InGaAs diodes indicates presence of some surface leakage
Summary
RADIATION THERMOMETERS are widely used in non-contact temperature measurement systems where the target is inaccessible, for example due to the extremely high temperatures in a blast furnace or to prevent contamination in semiconductor wafer growth [1]-[3]. In cases where the emissivity is not obtained, or when there is additional attenuation caused by the presence of an unwanted medium, such as smoke or steam, a two wavelength band or a ratio thermometer can be used to correct for the losses. The ratio thermometer works if the emissivity (and the attenuation factor) is the same across the two chosen wavelength bands [4]. In this case the reduction in signal due to reduced emissivity or attenuation cancels and the ratio of electrical outputs from the two photodetectors is a function of source surface temperature alone [5]. The Si-InGaAs photodetector (such as K1713 from Hamamatsu) has been used in a typical single spot ratio thermometer
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