Drift Rate and Precipitation of Lithium in Germanium

During the study of P-I-N Ge (Li) junctions to be used for gamma-ray spectrometers, it appeared that the drift process of Li+ ions is strongly depending on the nature of the raw materials: in similar conditions, the maximum width of the compensated region can change from less than 1 mm to more than 5 mm. The influence on drift rate of several factors is studied : resistivity, nature of acceptors (Ga, In, Zn), lifetime of minority carriers, copper diffusion. Attention is given to lithium precipitation. Using different thermoelectric probes (described) the concentration of Li+ ions and the rate of precipitation can be measured. The effect of lithium precipitation on drift rate is discussed.