Photocapacitance (phcap) investigation of proton irradiated si-pin diodes

This paper presents the first results of a photocapacitance investigation applied to the deep levels introduced by the 1.1 MeV proton bombardment into the Si PIN diodes. The ion density spectra asymptotic to the saturating value are measured at each wavelength using the forward injection in the dark in order to neutralize each deep level before photoexcitation. The present PHCAP method reveals the presence of proton-induced deep donors at 0.44 and 0.52 eV below the conduction band and a monotonic increase of the level density with increasing proton dosage. The Ec - 0.79 eV deep level is detected even in virgin crystals, regardless of the proton irradiation. The PHCAP measurements after photoexcitation reveal the photoinduced emissions and capture characteristics of these deep levels and prove the photoinduced deionization of the ionized deep donors at 0.70-0.74 and 0.35-0.38 eV above the valence band. By varying the initially irradiating photon energy, the excitation PHCAP measurements also reveal the neutral state of the 0.38 eV + Evionized level to be 0.83 eV below the conduction band. From the PHCAP results on the emission and capture characteristics of the deep levels, it is shown that the amount of the Frank-Condon shifts (dFC) of Ec- 0.44, 0.52, and 0.83 eV level are 0, 55, and 35 meV, respectively.