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Irradiation of silicon power rectifiers with electrons of 12 MeV energy has been carried out. Minority carrier lifetime τ, forward voltage V F , reverse recovered charge Q RR , reverse recovery time t RR for the diodes, circuit commutated turn-off time t q , and on-state voltage V T for the thyristors are measured as a function of dose. Power diodes and thyristors obtained from 〈111〉 neutron transutation or phosphorus doped float-zone silicon slices having 120Ωcm and 65Ωcm starting resistivity respectively and Ga-diffused are irradiated at room temperature. A linear relationship between carrier lifetime of irradiated diodes and electron dose is found and the calculated damage coefficients are k τ = 1.1x10 -8 cm 2 /s and 7.2x10 -9 cm 2 /s for the low-level and high-level lifetimes respectively at 25°C. For irradiated thyristors the linear relationship between turn-off time and dose yields k tq = 3x10 -9 cm 2 /s at 125°C. Electron irradiation also affects the resistivity of the starting n-type silicon, increasing it of ≈ 15Ωcm for radiation doses > 1×10 4 Gy. A dose rate effect on the electrical characteristics of the devices using pulses of different duration is analyzed. Annealing studies are carried out at 150 °C, 200°C and 360°C to assess the stability of the defects produced by the electron bombardment by monitoring the variation of the electrical characteristics of the irradiated devices in the temperature range of interest. DLTS measurements performed on electron irradiated power rectifiers have revealed a complex defect pattern. The E 1 defect level (E c -0.17 ev) is the principal recombination center that controls lifetime following room temperature irradiation. The energy levels and capture cross sections of these irradiation induced-defects are reported. This study confirms that lifetime control in silicon power devices is feasible by high energy electrons. The major advantages of this technique over metallic diffusion or 60 Co γ-irradiation methods are: better quality, lower processing cost and higher device yields. Annealing after irradiation is important to ensure long-term device stability.

In methanolic solution deaerated with argon or hydrogen, the pentacoordinated complex bromobis-(1,2-bisdiphenylphosphinoethane)cobalt(II)bromide, [Co(DPE)2Br]Br, where DPE = 1,2-bisdiphenylphosphinoethane, is reduced to Co(DPE)2Br by e-solv. For the reaction, Co(DPE)2Br+ + e-solv→Co(DPE)2Br, a value of k = (4.4±0.4) × 1010 mol-1 dm3 s-1 has been determined. Co(DPE)2Br rapidly loses Br-, with a rate constant of (8.0±0.4) × 105 s-1, to give the known compound Co(DPE)2+. Evidence has been obtained for reactions of Co(DPE)2Br+ with the radicals H, ·CH2OH and (CH3)2COH which lead, ultimately, to the same final product, namely Co(DPE)2+. Rate constants for the known reactions, Co(DPE)2++H2→CoH2(DPE)2+ and Co(DPE)2++CO→(CO)(DPE)2+ were found to be k=(3.0±0.2)×104 mol-1 dm3 s-1 and (1.4±0.1)×104 mol-1 dm3 s-1 respectively. Bis-(1,2-bisdiphenylphosphinoethane)rhodium(I)chloride, [Rh(DPE)2]Cl, bis-(1,2-bisdiphenylphosphinoethane)rhodium(I)perchlorate, [Rh(DPE)2]ClO4, and bis-(cis-1,2-bisdiphenylphosphinoethylene)rhodium(I)chloride, [Rh(VPP)2]Cl, where VPP=cis-1,2-bisdiphenylphosphinoethylene, react with e-solv in methanolic solution deaerated with Ar. For the reactions Rh(DPE)2+ + e-solv→Rh(DPE)2 and Rh(VPP)2++e-solv→Rh(VPP)2 values of k=(3.0±0.3)×1010 mol-1 dm3 s-1 and (2.8±0.2)×1010 mol-1 dm3 s-1 respectively, have been calculated. The products of both reactions show an absorption band in the visible region (λmax=600 nm, ϵ600= (4.0±0.2)×103 mol-1 dm3 cm-1) and decay to the original compounds; this decay is ascribed to reaction with the solvent, viz. Rh(diphosphine)2+CH3OH→Rh(diphosphine)2++Products, where the rate constant is k=(3.6±0.3)×102 s-1 when diphosphine=DPE and k=(1.3±0.2)×103s-1 when diphosphine=VPP.