Long living excited states in boron doped diamond

Abstract

Long living excited states in boron doped diamond are detected by photoconductivity and photoconductivity excitation spectroscopy at temperatures T<190 K in the energy regime 3.2–3.5 eV. The photoconductivity spectra show pronounced maxima in highly doped [(4–8)×1018 cm−3] diamond which decrease with decreasing doping density. A model is presented where holes are optically excited from compensating deep defects, 3.36 eV above the valence band edge, into the valence band. Here they get captured by LO phonon emission into long living excited levels of boron. The long living excited states are 200, 240, and 266 meV above the 1s ground level. Maxima in photocurrent can be detected at high doping concentrations as the wave function overlap between neighboring excited states is significant to allow hopping transitions between neighboring excited states.