Description:
<jats:p>New deep acceptors (DA) at Ev+80 meV together with contaminating substitutional copper (Cus) were produced in Ge by the quenching from 700 °C. Annealing around 260 °C caused these acceptors to disappear leaving an equal additional Cus density, giving rise to a decrease in hole mobility at 77 K. The annealing process obeys first-order kinetics with an activation energy of 1.3 eV. Annealing behavior consistently explains the so-called reverse annealing of quenching-induced conductivity changes that have often been observed by various investigators. In the as-quenched state, the DA density is completely proportional to the Cus density, which was varied at 700 °C from 3×1013 to 3×1015 cm−3 using the techniques of gettering and diffusion of copper. The 1.5 MeV electron irradiation to a total dose of 5×1014 electrons/cm2 slightly below room temperature induced the DA acceptors once annihilated by the preceding annealing to reappear in a density of 2×1013 cm−3. The most probable defect model for the DA acceptor which best fits the data is a pair consisting of a substitutional copper atom and a mobile defect, which may possibly be a vacancy or an interstitial of a neutral impurity like carbon, silicon, or oxygen.</jats:p>