John Bartko

Electron irradiation induced recombination centers in silicon-minority carrier lifetime control

Recombination centers introduced in silicon p+-n-n+structures by irradiation with 2-MeV electrons are studied by measuring minority carrier lifetime and annealing kinetics. The approximate location of these recombination centers in the forbidden gap and their densities are obtained by the thermally stimulated current method. The results identify one defect as a divacancy with an energy level of Ev+ 0.26 eV. Possible identities of other deep levels are discussed. The technique of minority carrier lifetime control by electron irradiation has been developed into a reliable manufacturing process for power devices.

Highly conductive poly(phenylene sulfide) prepared by high‐energy ion irradiation

Ion irradiation of poly(phenylene sulfide) (PPS) films with various ions produces highly conductive films. Using 5.6‐MeV fluorine ions, the conductivity of irradiated films at a dose of 1×1016 ions/cm2 is comparable to chemically doped films (0.77 S/cm), and higher conductivities should be possible with higher doses. Iodine ions of 50 MeV produced films with similar conductivities at a dose of 1×1014 ions/cm2: the highest conductivity reported for an organic material irradiated by such a low dose. Films irradiated with 0.32‐MeV lithium ions did not change their conductivity up to 1×1015 ions/cm2. We attribute the higher conductivities obtained in our iodine irradiated films to the substantially higher electronic energy deposition associated with 50‐MeV I ions. The Li‐implanted films showed no substantial change in conductivity probably because their energy deposition rates are too low.

Ion-induced conductivity in poly (phenylene sulfide)

New data on the production of electrical conductivity in poly(phenylene sulfide), PPS, by ion irradiation are presented. These and previously reported PPS data are investigated in the framework of a theoretical semiempirical model that relates observed conductivity to parameters associated with the deposition of energy in the polymer by the bombarding ions. It is shown that the onset of conductivity with increasing ion dose is dependent on overlap of individual ion damage regions. A straight line relationship is obtained between log of the ion stopping power and log of the effective overlap radius of the ion damage regions. Furthermore, the magnitude of the values of effective overlap radii are consistent with physical observations and theoretical predictions. At higher ion doses, the rapid increase in conductivity appears to be consistent with a multistage reaction mechanism for the production of conducting species in the polymer. A universal curve of conductivity as a function of dose above threshold dose is seen to fit all of the PPS data up to a dose of a factor of 50 above threshold. This curve and the predictable behavior of the threshold dose allow the selection of ion/dose combinations to produce a desired conductivity.

Radiation-hard static induction transistor

The design, fabrication, and characteristics of a 350-V, 100-A buried-gate static induction transistor (SIT) as a power switching device for applications in military and space environments because of its potential for radiation hardness, high-frequency operation, and the incorporation of on-chip smart power sensor and logic functions are described. The potential radiation hardness of this class of devices was evaluated by measurement of SIT characteristics after irradiation with 100-Mrad (2-MeV) electrons and up to 10/sup 16/ fission neutrons/cm/sup 2/. High-temperature operation and the possibility of radiation damage self-annealing are discussed. >