Photocapacitance (PHCAP) Investigation of Proton Irradiated Si‐PIN Diodes

Abstract

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 + Ev ionized 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) ofEc -0.44, 0.52, and 0.83 eV level are 0, 55, and 35 meV, respectively.

Photocapacitive Determination of Spatial Distribution of Deep Levels at Si / SiO2 Interfaces

“…PHCAP measurements.-In order to determine the values of the level density and activation energy for the interface deep levels of a MOS structure, we applied the PHCAP method under a constant capacitance condition. As reported by the authors, 14,15 the photocapacitance method has many advantages over other thermal-excitation methods such as DLTS because of its optical excitation at a constant low temperature. In addition, the PHCAP method under a constant capacitance condition enables accurate determination of the depth profiling of the deep level density, because the depletion layer thickness is kept constant regardless of the change of ion densities.…”

“…One of the present authors (J.N.) has applied this method to Au-diffused Si diodes, 14 protonirradiated Si-PIN diodes, 15 and III-V compounds [16][17][18][19] to reveal deep levels in the bulk region of each material. Recent PHCAP results have shown detailed spatial distribution of MeV proton-induced deep levels in Si applying the constant capacitance method.…”

Deep levels and minority carrier lifetime in proton irradiated silicon pin diode

“…3 In order to obtain the correct ion density and the activation energy of deep levels, all of the filled carriers have to be excited by monochromatic light illumination. Varying the irradiating wavelength to longer wavelengths after photoexcitation is known to be an excellent technique ͑zigzag control method͒ to investigate the characteristics of optical transition in semiconductors.…”

Terahertz Pioneer: Jun-ichi Nishizawa “THz Shogun”

“…The author cannot hope to site more than a few of the 300 plus papers that he authored between 1990 and present day (more than 120 as first author). These included papers on crystal growth [126], p-i-n [127] and photo diodes [128], molecular layer epitaxy [129], photo-quenching [130], Raman lasers [131], MOCVD [132], new diode structures [133], surface chemistry [134], silicon device physics [135], semiconductor luminescence [136], high power SIT devices [137], growth of IV-VI semiconductors [138], GaAs growth and doping [139], thin film deposition [140], Raman amplifiers [141], and even some politically prescient work on atmospheric CO [142].…”