Mean free drift length of holes in radiation damaged germanium detectors

For radiation damaged HPGe detectors, the mean free drift length of holes λh is a useful parameter to characterize the defect structures in the germanium crystal. λh 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 λh on these parameters. Our data reveal that λh follows a square root function of the hole current. In respect to the magnitude of the electrical field E, λh possesses two components: one linear in E and the other rising as E3/2. These dependencies of λh on hole current and temperature favor the defect model of Disordered Regions over Isolated Defects, while the dependence of λh on electric field strength is beyond these simplistic defect models