We have studied the effects of 16-Me V proton irradiation on the performance of a variety oflight emitting diodes (LEO's) emitting between 820 and 1300 nm. Total light output and current were measured at room temperature as a function offorward bias prior to and following a sequence of room temperature l6-MeV proton irradiations. Our results indicate that the relative amount of proton-induced degradation from one LEO type to another is similar to that observed for neutron and gamma irradiations. More specifically, the most sensitive device is the amphoterically Si-doped GaAs LEO which is characterized by a long preirradiation minority carrier lifetime. The most resistant LEOs are the high radiance GaAIAs (820 nm) and InGaAsP (1300 nm) LEOs. As in the case of Si devices, the degradation rate per irradiating particle ftuence is significantly greater for proton irradiation of these LEOs than it is for neutron exposure.Neutron damage data presented herein indicate that the ratio of proton-to-neutron degradation rates can be as high as 100. Lifetime-damage constant products for constant current operation ate calculated for each LEO type and vary from 1.5 X 10-13 cm 2 /p for the InGaAsP LEO to 1.1 X 10-JO cm 2 /p for the amphoterically Si-doped GaAs LEO.
The application of fiber optic links in both commercial and military space systems, as
Photoluminescence measurements have been performed at 4.2 K between 1.2 and 1.6 eV on compensated high-resistivity CdTe containing from 1015 to 1018 cm−3 indium. A series of phonon-coupled emission bands with a no-phonon peak at 1.454 eV is dominant in most samples and grows in intensity with increasing In concentration. On the basis of the compensation model, the 1.454-eV emission is attributed to radiative recombination at an [cadmium vacancy-In] acceptor complex. Comparison of the experimental results with this model suggests that the chemical equilibria governing formation of the acceptor complex are frozen in at approximately 500 K as the sample is cooled from the growth temperature. The existence of significant changes at 500 K in the mobility of defects related to the acceptor complex is confirmed by the observation of a prominent growth in the 1.454-eV emission at an annealing temperature of 500 K in A+-implanted n-type CdTe. Exciton emission in the CdTe : In samples is dominated by a narrow bound exciton band at 1.584 eV which is assigned to recombination at a center associated with In. Edge emission is relatively weak in all samples with the peak positions varying from 1.538 to 1.546 eV.
Microelectromechanical sensors, ADXL5O and XMMAS40G accelerometers which are fabricated with surface micromachining techniques are characterized for their total dose radiation response. Different failure mechanisms were observed when the sensor element or the whole device was irradiated.
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