In-Situ Gamma Radiation Testing of 2.4 Micron Wavelength Extended InGaAs Photodiodes at Dry Ice Temperatures (2024)

  

Abhay M. Joshi *1 , Shubhashish Datta 1 , Nilesh Soni 1 , Michael Sivertz 2 , and James Jardine 3
1 Discovery Semiconductors Inc., Ewing, NJ, USA
2 NASA Space Radiation Laboratory, Brookhaven National Laboratory, Upton, NY, USA.
3 Brookhaven National Laboratory, Upton, NY, USA.

ABSTRACT

Multiple space applications require infra-red photodiodes, including spectroscopy, optical communication links, and rapid Doppler shift LIDAR. Extended InGaAs photodiodes with 2.4-micron cutoff wavelength have been recently shown to be resilient to irradiation with Protons, Alpha Particles, Carbon Ions, and Iron Ions for fluence levels corresponding to multi-year Low Earth Orbit, Geostationary, inter-planetary, and deep space missions. Our prior studies have shown that the radiation-induced displacement damage may lead to some elevation in photodiode’s leakage current, without significant sign of ionization damage. To further confirm this finding, these devices were subjected to Gamma rays to explicitly measure the effect of ionization damage only.

We have successfully tested 290 µm diameter, 2.4-micron wavelength, Extended InGaAs photodiodes coupled with single mode fiber for gamma radiation. Three devices were cooled to dry ice temperatures (~ -71° C) and subjected to two rounds of 662 keV gamma rays from Cesium-137 for 15 krad (water) for a cumulative dose of 30 krad (water). The devices were reverse biased at 100 mV and their leakage current was monitored in-situ to simulate their function as exposed to radiation in space environment. The in-situ data showed slight increase in leakage current in the presence of gamma radiation, and returned to original value once the gamma rays were turned off, thus proving the resilience of Extended InGaAs Photodiodes to ionization damage. These results were corroborated with detailed pre- and post-radiation measurements, which also demonstrated unchanged quantum efficiency and bandwidth over a wide range of operating temperatures, from -71 °C to +20 °C.

INTRODUCTION

Several space applications require Near Infra-Red (NIR) and Short Wave Infra-Red (SWIR) photodetectors with diverse set of requirements. Spectroscopic missions require photodiodes with spectral coverage from 900 nm to 2300 nm. These applications require large area devices having low leakage current and high shunt impedance to detect weak back-scattered light with high signal-to-noise ratio. The speed requirements for such spectroscopic applications are at most in megahertz range. In contrast, space-based optical communications at 2-micron wavelength, enabled by advances in Holmium and Thulium-doped lasers, require several Gigahertz of bandwidth. Coherent lidar is another application that benefits from photodiodes having high optical power handling for shot noise limited performance, and > 4 GHz bandwidth to accommodate Doppler shift seen in Low Earth Orbit (LEO). Extended InGaAs photodiodes with 2.4-micron cutoff wavelength have been previously demonstrated to satisfy these system requirements [1 – 3].

Diversity of radiation environment for various space missions, from LEO satellites to deep space missions outside Earth’s protective magnetosphere, requires testing these photodiodes with a wide range of particles. Extended InGaAs photodiodes have passed irradiation with Protons, Alpha Particles (Helium Ions), Carbon Ions, and Iron Ions for fluence levels corresponding to multi-year Low Earth Orbit, Geostationary, inter-planetary, and deep space missions [1 – 3].

Irradiation with high energy ions can produce both displacement and ionization damage in photodiodes. Our prior studies have shown that the radiation-induced displacement damage may lead to some elevation in photodiode’s leakage current, and does not have any other adverse impact on the device performance. Also, none of the prior radiation tests demonstrated any significant sign of ionization damage. In this work, three Extended InGaAs photodiode modules were cooled to dry ice temperature (~ -71 °C) and subjected to 662 keV Gamma rays up to a Total Ionizing Dose (TID) of 30 krad (water) to explicitly measure the effect of ionization only.

REFERENCES


Event: SPIE Defense + Commercial Sensing, 2024, National Harbor, Maryland, Proc. of SPIE Vol. 13049, Paper 130490K, 2024.