Mean free drift length of holes in radiation damaged germanium detectors

For radiation damaged HPGe detectors, the mean free drift length of holes /spl lambda//sub h/ is a useful parameter to characterize the defect structures in the germanium crystal. /spl lambda//sub h/ depends on three parameters: temperature, electrical field strength, and internal hole current. Multiple measurements with different sets of parameters were carried out to study the functional dependence of /spl lambda//sub h/ on these parameters. Our data reveal that /spl lambda//sub h/ follows a square root function of the hole current. In respect to the magnitude of the electrical field E, /spl lambda//sub h/ possesses two components: one linear in E and the other rising as E/sup 3/2/. These dependencies of /spl lambda//sub h/ on hole current and temperature favor the defect model of Disordered Regions over Isolated Defects, while the dependence of /spl lambda//sub h/ on electric field strength is beyond these simplistic defect models.