Radiation testing of 2.4 micron wavelength extended InGaAs photodiodes for galactic cosmic rays

Abstract

We have successfully tested simultaneously 2.4 Micron Wavelength, Extended InGaAs Photodiodes having diameters of 20, 30, 40, 50, 100, 150, 200, 250 and 290 Micron, coupled with a Single Mode Fiber using Hydrogen (H), Helium (He), and Iron (Fe) Ions which collectively make up over 90% of the Galactic Cosmic Rays (GCR). During irradiation, the devices were maintained at dry ice temperature, reverse biased at 100 mV, and their leakage current was continuously monitored in-situ during the run. After the exposure was completed, all nine devices were monitored for any change in their leakage current at 100 mV and room temperature for several weeks to monitor any annealing effects that may occur. Nine Photodiodes with the above varying diameters were radiated with 100, 250, 500 and 1000 MeV/n Hydrogen, Helium, and Iron Ions with a fluence of 10⁶, 10⁷ and 10⁸ ions/cm² at each energy level. Pre- and Post-radiation results were also measured for: (1) Leakage Current Vs. Voltage for the InGaAs Photodiodes; (2) Responsivity (Quantum Efficiency) in A/W for Photodiodes; and (3) Bandwidth of the Photodiodes. All devices were found to be fully functional at the normal operating conditions and at both dry ice and room temperature. We did not observe any post radiation annealing effect for leakage current at room temperature and 100 mV bias for any of the devices after several weeks of data logging.