A coherent model for deep-level photoluminescence of cu-contaminated n-type gaas single crystals

Abstract

A comparative study of the 77 K PL spectra of about one hundred n-type GaAs single crys-tals, grown by the horizontal or Czochralski technique, shows that the principal native defects in the former (in the “as-grown” state) are As-vacancies, whereas Ga-vacancies are dominating the latter (2). Besides the VGa, copper appears as the major acceptor contaminant in these crystals and is respon-sible for the 0.83 eV peak. Association of Cu and/or V_Ga with V_As and/or dopant atoms tends to neutralise this compensation. Considering the contradicting attributions found in the literature, new definitions of the nature of some centers responsible for the deep-level PL were needed to fit with the experimental da-ta. Thus the center yielding the 1.35 eV, PL-band, usually identified as substitutional copper, has to be defined here as the As-va-cancy associated defect complex: (V_As+Cu=V_As+) Similarly the 1.295 eV PL is associated with the (Te+Cu=V_As+ complex and the often en-countered level at 1.22 eV is identified as the (Si+Cu=V_As ⁺) complex. These levels, to-gether with the better known ones at 0.83, 0.96, 1.02, 1.17, 1.19 eV are linked in a coherent model which can account for the ap-pearance and the relative amplitude of the different PL peaks observed, as a result of the doping and the thermal history of the crystals during growth.