Differential Hall analysis of the carrier profile in germanium due to the doping effect of as-implanted boron

The doping effects at low temperatures need to be explored for three-dimensional integration of semiconductor devices. A differential Hall technique was developed in this study to investigate the doping effects of as-implanted boron in germanium. A current-conducting path was established in the test structure before boron implantation, which led to the observed doping effect. Considering the etch rate affected by the implantation damage, the thickness reduction of germanium was monitored at each etching step during the differential Hall measurements. After boron implantation at a dose of 10¹⁵ cm⁻², a surface hole concentration exceeding 10¹⁹ cm⁻³ was observed. However, the carrier concentration decreased with depth, deviating from the chemical boron implantation profile. The sheet carrier concentration slightly increased with successive annealing at temperatures increasing from 100 to 550 °C, indicating the stability of the doping mechanism.