Impact of high energy particle irradiation on the electrical performance of Si_1−x Ge _x epitaxial diodes

Abstract

The impact of 20-MeV alpha ray irradiation on the electrical characteristics of strained-layer epitaxial Si_1−x Ge _x diodes is investigated as a function of fluence and Ge content (x = 0.08, 0.12 and 0.16). The reverse current at a fixed bias increases with fluence, although the rate of increase decreases with increasing fluence and/or Ge content. The reduction of the capacitance with fluence points to a strong deactivation of the boron (B) dopant atoms, which decreases with increasing Ge content. The close to square root dependence between the B-deactivation and the reverse current increase, suggests that in the irradiated diodes the latter is dominated by deep levels associated with interstitial B complexes. This is confirmed by deep level transient spectroscopy, revealing that the trap introduction rate at a given fluence reduces with increasing Ge content, similar to that for the reverse diode current.