Investigation of neutron-produced defects in silicon by transconductance measurements of junction field-effect transistors

Defects introduced in silicon by neutron irradiation were investigated by measuring the phase angle ϑ of the small-signal transconductance of the junction field-effect transistors (JFET). Measurements of ϑ as a function of frequency allowed the determination of the time constant for each defect. From the temperature dependence of the time constant, assuming that capture cross sections are independent of temperature, the energy levels of Ev+0.19 and Ev+0.35 eV in p-type silicon and Ec−0.16, Ec−0.19, and Ec−0.44 eV in n-type silicon were obtained. For these defects, calculations gave majority-carrier capture cross-section values of 2.8×10−15 and 1.1×10−14 cm2 in p-type silicon, and 3.9×10−14, 1.6×10−16, and 2.3×10−14 cm2 in n-type silicon, respectively. Comparing with other published data, it was found that the energy level of Ec−0.44 eV showed the value between the previously reported energy levels of Ec−0.4 and Ec−0.5 eV correlated with the doubly negative charge state and singly negative charge state of the divacancy, respectively. Thus, it is believed that a total of six energy levels are introduced in silicon by neutron irradiation. The energy levels of Ec−0.16 and Ev+0.35 eV were found to be correlated with the A center and the divacancy, respectively.