Radiation Testing of 2.4 Micron Wavelength Extended InGaAs Photodiodes for 100 MeV/n Carbon Ions (2022)

  

Abhay M. Joshi *1 , Shubhashish Datta 1 , Jeff Mertz 1 , Nilesh Soni 1 , Michael Sivertz 2 , Adam Rusek 2 , Trevor Olsen 2 , 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

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 100 MeV/n Carbon (C) Ions up to a cumulative dose of ~40 Krads. 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 MeV/n Carbon Ions with a fluence of 106, 107, 108, 109, and 1010 ions/cm2 at each fluence level. At 100 MeV/n the Linear Energy Transfer (LET) of Carbon Ion is ~0.156 MeV-cm2/mg in Extended InGaAs, which is an order magnitude more than Proton (H) and Helium (He) Ions of 100 MeV/n energy. Thus, significant displacement damage is anticipated in the Extended InGaAs Photodiode with 100 MeV/n Carbon Ions with a total fluence of 1 × 1010 ions/cm2.

Pre- and Post- radiation results were also measured for: (1) Leakage Current Vs. Voltage for the Extended 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. The leakage current increased up to a factor of ~2X at lower bias of 100 mV at the highest fluence of 1010 ions/cm2, but not significantly at higher bias of 2 V. 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.

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 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 >4 GHz bandwidth, thus covering Doppler shift seen in Low Earth Orbit (LEO). Diversity of radiation environment for various space missions, from LEO satellites to deep space missions outside Earth’s protective magnetosphere, requires testing photodiodes with a wider range of particles.

Our prior work on Standard and Extended InGaAs photodetectors have addressed a number of challenging space applications using a combination of space flights and comprehensive radiation testing in laboratory. Here, we present Extended InGaAs Photodiodes having 2.4 Micron cutoff wavelength with diameters ranging from 20 Micron to 290 Micron, that have successfully passed irradiation with 100 MeV/n Carbon Ions up to a fluence of 1 × 1010/cm2, corresponding to a Total Ionizing Dose (TID) of 41.5 krad (water).

Dual Depletion Region (DDR) photodiode structure lends itself to low leakage current, low capacitance, high bandwidth, and increased resilience to radiation. Recently, the DDR structure was applied to the lattice-mismatched InGaAs / InP material system to produce 2.4 micron wavelength photodiodes that have passed several radiation tests. These photodiodes have successfully withstood 50 MeV Proton radiation up to a fluence of 1011/cm2, which corresponds to over 10 year of mission life for typical remote sensing LEO spacecrafts [1]. The Extended InGaAs photodiodes were subsequently tested with high energy Protons, Alpha Particles (Helium Ions), and Iron Ions, thus simulating exposure to Galactic Cosmic Rays (GCR) in multi-year interplanetary or deep space missions [2]. The potential impact of a particle incident on a material is determined by the amount of kinetic energy transferred from the radiating particle to the material, i.e. Linear Energy Transfer (LET). The severity of a radiation run is given by the product of the LET and the number of irradiating particles per unit area, i.e. Fluence. The 100 MeV/n Carbon Ion radiation results described here constitute the most severe radiation test to which the Extended InGaAs Photodiodes have been exposed.

REFERENCES


Event: SPIE Optical Engineering + Applications, San Diego, CA, Proc. SPIE, Vol. 12234, Paper 1223408, 2022.

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