Defect engineering for shallow n‐type junctions in germanium: Facts and fiction

Abstract

An overview is given on the status of n‐type dopant activation and diffusion in Ge, based on a standard ion implantation and annealing scheme. Emphasis is on defect engineering approaches to optimize either or both parameters. A detailed discussion is given on the use of co‐implantation by neutral or other n‐type dopants. As a case study, the impact of the C ion implantation energy and dose on n‐type junctions in p‐Ge by P + C co‐implantation will be given. It is demonstrated that for fixed P implant conditions, there exist an optimum energy and dose for achieving a minimum junction depth by the formation of C–PV complexes. An alternative approach is the use of self‐interstitial management at the end‐of‐range of the P implantation. Finally, an overview is given of alternatives for obtaining shallow, highly activated n‐type junctions in Ge. They rely on: non‐standard implantation schemes, ultra‐short annealing methods or relying on in situ doped epitaxial deposition.

Diffusion and Dopant Activation in Germanium: Insights from Recent Experimental and Theoretical Results

“…The dominance of V is established experimentally [28] and is important as it mediates the diffusion of most dopants in Ge [5,41,42]. Concerning donor atom diffusion, previous studies have established that n-type dopants such as P, As, and Sb diffuse in Ge via a vacancy mechanism at a rate that is faster than self-diffusion [41][42][43][44][45]. It should be considered that the relatively fast transport of n-type dopants is not appropriate for the formation of ultra-shallow donor profiles.…”

Interface Control Processes for Ni/Ge and Pd/Ge Schottky and Ohmic Contact Fabrication: Part One

“…Electrons in solids obey Fermi-Dirac statistics. At low temperatures, the distribution of electrons over a range of allowed energy levels at thermal equilibrium is given by, fE ðÞ ¼ 1 1 þ e EÀE F ðÞ =k B T (1) where, k B is the Boltzmann constant. The function, f(E) is the Fermi-Dirac distribution function which gives the probability that an available energy state, E will be occupied by an electron at temperature, T on the Kelvin scale.…”

“…In order to produce high speed devices, n-type germanium is preferred over p-type germanium because electrons have a higher mobility than holes. However, the doping levels in n-type germanium are low [1]. The second major limitation is that it is difficult to produce Ohmic contacts on ntype germanium [2][3][4][5][6][7] because of Femi-level pinning.…”

Phosphorous Diffusion in N2+-Implanted Germanium during Flash Lamp Annealing: Influence of Nitrogen on Ge Substrate Damage and Capping Layer Engineering

“…1,2 The main reason is the fast n-type dopant (P, As, Sb) diffusion in Ge, which takes place via a vacancy-mediated mechanism. 3 The parallel significant out-diffusion trend of P, As or Sb in Ge leads to enhanced dopant dose loss, which, together with clustering phenomena, constitute additional problems for achieving high activation levels.…”

“…These can be divided in specific categories, the most representative being: (a) co-implants with impurities such as carbon, 1,4 fluorine 5,6 or nitrogen, 7,8 (b) co-doping with other n-type dopants such as arsenic or antimony, 9,10 (c) non-conventional approaches such as low temperature metal-induced dopant activation, 11 and bulk interstitial injection by GeOx clusters disolution. 12 The majority of these approaches have been recently summarized and reviewed by Simoen et al 1 The diffusion of n-type dopants in Ge is highly influenced by the following three experimental parameters.…”