p-type doping of Ge by Al ion implantation and pulsed laser melting

Germanium recently attracted a renewed interest for its potential applications in severalfields such as nanoe-lectronics, photonics, plasmonics, etc., but well-known issues about doping at high concentration and controllingimpurity profiles prevent its integration in technology. To this purpose, p-type doping aluminum ion im-plantation followed by pulsed laser annealing in the melting regime has been investigated for thefirst time. Inparticular, two different regimes have been studied, in order to explore the limit of incorporation for such amethod: 6.4 × 1014Al/cm2and 4.2 × 1015Al/cm2, both at 25 keV, corresponding to concentrations below andabove the solid solubility, respectively. We found that in the former case, oxygen contamination precludes fullactivation (< 60%), as suggested by Raman characterizations. Besides, secondary ion mass spectrometry evi-dences pronounced out-diffusion and pile-up of the dopant near the surface. In the letter case, remarkable(~1 × 1020Al/cm3), although partial (~30%), electrical activation is obtained, independently on O occurrence.Therefore, O-Al and Al-Al clustering are proposed as concurrent mechanisms, limiting full activation at highimplanted dose. Nevertheless, the samples display good crystalline quality and, surprisingly, a significantthermal stability (up to 600° C).