The basic mechanisms of space radiation effects on microelectronics are reviewed. Topics discussed include the effects of displacement damage and ionizing radiation on devices and circuits, single-event phenomena, dose enhancement, radiation effects on optoelectronic devices and passive components, hardening approaches, and simulation of the space radiation environment. A summary of damage mechanisms that can cause temporary or permanent failure of devices and circuits operating in space is presented. >

Radiation effects on microelectronics in space

Charge-collection measurements on GaAs MESFET test structures demonstrate that more charge can be collected at the gate than is deposited in the active layer and more charge can be collected at the drain than the total amount of charge produced by the ion. Enhanced charge collection at the gate edge has also been observed. The current transients produced by the energetic ions have been measured directly with about 20-ps resolution. The significance of this work is that it shows charge-collection phenomena in GaAs MESFETs to be very complex with important implications for modeling SEU (single-event upset) phenomena and developing techniques to mitigate SEU effects. >

Ion induced charge collection in GaAs MESFETs

The single-event upset (SEU) characteristics of GaAs devices and circuits are reviewed. GaAs FET-based integrated circuits (ICs) are susceptible to upsets from both cosmic-ray heavy ions and protons trapped in the Earth's radiation belts. The origin of the SEU sensitivity of GaAs ICs is discussed in terms of both device-level and circuit-level considerations. At the device level, efficient charge-enhancement mechanisms through which more charge can be collected than is deposited by the ion have a significant negative impact on the SEU characteristics of GaAs ICs. At the circuit level, different GaAs digital logic topologies exhibit different levels of sensitivity to SEU because of variations in parameters, including logic levels, capacitances, and the degree of gate or peripheral isolation. The operational and SEU characteristics of several different GaAs logic families are discussed. Recent advances in materials and processing that provide possible solutions to the SEU problem are addressed.

Single-event phenomena in GaAs devices and circuits

Funneling-current transients produced in semiconductor devices are predicted to occur on a picosecond time scale. We have measured these transients using a high bandwidth sampling system. Measurements were made on 1, 3, and 10 ?-cm silicon low capacitance diodes and 1016 cm-3 Te-doped GaAs diodes. The data is compared to the Hsieh, Murley and O'Brien, the McLean and Oldham, and the Messenger models. Risetime versus doping density, peak current, total charge, and amplitude versus bias were measured. Also, current transients and prompt charge versus energy are presented.

Transient Measurements of Ultrafast Charge Collection in Semicouductor Diodes

Focused electron-beam pulses have been used to study and compare collection of ionization generated charge by the gate and induced drain current in GaAs field-effect transitors. Results indicate that hole collection by the gate occurs principally by diffusion, and that built-in fields at the channel-substrate junction inhibit this collection except at the device edges where the gate directly contacts the semi-insulating substrate. At sufficiently high excitation levels the induced drain current is dominated by photoconduction through the substrate from source to drain, and is enhanced by inherent photoconductive gain. The large magnitude of the drain current response relative to the gate collection suggests that it is an important effect for single-particle events in GaAs devices.

Gate Charge Collection and Induced Drain Current in GaAs FETs

Results of charge collection measurements on technologically important GaAs devices fabricated on semiinsulating (SI) substrates are described Data are presented which suggest that charge funneling in SI GaAs is relatively unimportant compared to that which occurs in semiconducting silicon and GaAs A qualitative comparison is made of charge collection in silicon and SI GaAs devices to examine their relative susceptibility to single-event upset

J. R. Srour

Papers

Charge Collection Measurements on GaAs Devices Fabricated on Semi-Insulating Substrates