Formation of hydrogen-related shallow donors in Ge_1-xSi _x crystals implanted with protons

It is found that shallow hydrogen-related donors are formed in proton-implanted dilute Ge_1-xSi_x alloys (0 ≤ × ≤ 0.031) as well as in Si-free Ge samples upon heat-treatments in the temperature range 225-300°C. The maximum concentration of the donors is about 1.5×10¹⁶ cm^-3 for a H⁺ implantation dose of 1×10¹⁵ cm^-2. The temperature range of formation of the proton-implantation-induced donors is the same in Ge _1-xSi_x samples with different Si concentration. However, the increase in Si content results in a decrease of the concentration of the hydrogen-related donors. It is argued that the H-related donors could be complexes of Ge-self-interstitials with hydrogen atoms. The observed decrease in the concentration of the donors with an increase in Si content in the Ge _1-xSi_x samples is associated with interactions of mobile hydrogen atoms with Si impurity atoms. Such interactions reduce the number of implanted hydrogen atoms that can be involved in defect reactions resulting in the formation of H-related shallow donors.