Characterization of GaAsP trap detector for radiometric measurements in ultraviolet wavelength region

• Published in: Review of scientific instruments 2005-03, Vol.76 (3)
• Main Authors: Noorma, M., Kärhä, P., Lamminpää, A., Nevas, S., Ikonen, E.
• Format: Article
• Language: English
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.1866972

A trap detector was constructed of three Schottky-type 10×10mm2 GaAsP photodiodes. The spectral reflectance of the trap detector was calculated from the measured spectral reflectances of a single GaAsP photodiode in the wavelength range between 240 and 600nm, and compared to the measured spectral reflectance of the trap detector at three laser wavelengths. The absolute spectral responsivity of the trap detector was measured. The internal quantum efficiencies (IQE) of the trap detector and a single photodiode were calculated in the wavelength region between 250 and 400nm from the spectral reflectances and responsivities. The comparison revealed reduction of the apparent IQE of the trap detector as compared to the single photodiode at the level of 10%. The spatial uniformity of the responsivity of the trap detector was measured, and the corresponding uncertainty component at 325nm was calculated to be 4×10−4. The effect of moderate ultraviolet exposure at the level of 50mJ∕cm2 on the stability of the responsivity of GaAsP photodiode was studied and found to be below 2×10−3 at all used wavelengths.