germaniumdoping

Germanium doping refers to the intentional introduction of impurities into germanium to modify its electrical conductivity. Germanium is a group IV semiconductor with a relatively small band gap, historically used in early transistors and still present in high-speed and optoelectronic devices. Doping creates n-type material by adding donor impurities (for example phosphorus, arsenic, or antimony) and p-type material by introducing acceptor impurities (such as boron, aluminum, or gallium). These dopants provide extra electrons or holes that dominate conduction at room temperature, enabling predictable carrier concentrations.

Doping methods include diffusion of dopants into germanium, ion implantation followed by annealing to repair lattice damage and activate dopants, and in-situ doping during crystal growth (for example during Czochralski growth or molecular beam epitaxy). Germanium exhibits relatively rapid dopant diffusion compared to silicon at similar temperatures, which can complicate fabrication and require careful thermal budgets.

Dopant activation and carrier mobility determine device performance. Shallow donor and acceptor levels in germanium enable substantial conductivity at moderate temperatures, but the intrinsic carrier concentration in Ge is comparatively high due to its narrow band gap, leading to higher leakage currents in undoped or lightly doped devices.

Applications include germanium-based diodes and transistors, Ge/Si or Ge-rich heterostructures in high-speed electronics, photodetectors, and some solar cells. The ongoing development of Ge-containing materials emphasizes compatible doping strategies and thermal processing to achieve stable, well-defined dopant profiles.