Ionization mechanisms of aluminum acceptor impurity in silicon

Abstract

Processes of ionization of shallow acceptor centers (ACs) in silicon are studied. In crystalline silicon samples with phosphorus (1.6×1013, 2.7×1013, and 2.3×1015cm−3) and boron (1.3×1015cm−3) impurities, μAl impurity atoms were produced by implantation of negative muons. It is found that thermal ionization is the main mechanism for ionizing the Al acceptor impurity in both p-type and n-type silicon with an impurity concentration of ≲1015cm−3 at T>45 K. The thermal ionization rate of Al ACs in Si varies from ∼105 to ∼106s−1 in the temperature range 45–55 K.