Metal/P-Type Gesn Contacts With Specific Contact Resistivity Down To 4.4x10(-10) Omega-Cm(2)

Ga and Sn surface-segregated p+-GeSn (Seg. p+-GeSn) was grown by molecular beam epitaxy (MBE) to achieve an average active Ga doping concentration of 3.4x10(20) cm(-3) and surface Sn composition of more than 8%. This enables the realization of record-low specific contact resistivity.c down to 4.4x10(-10) O-cm(2). The average.c extracted from 14 sets of Ti/Seg. p+-GeSn Nano-TLM test structures, a collection of more than 90 devices is 6.5x10(-10) Omega-cm(2). This is also the lowest.c for non-laser-annealed contacts. Ti contacts to p+-GeSn films with and without Ga and Sn surface segregation were fabricated. It is shown that the segregation of Ga and Sn at the Ti/p+-GeSn interface leads to 50% reduction in.c as compared with a sample without segregation.