N-type doping of Ge by As implantation and excimer laser annealing

Abstract

The diffusion and activation of arsenic implanted into germanium at 40 keV with maximum concentrations below and above the solid solubility (8 x 10(19) cm(-3)) have been studied, both experimentally and theoretically, after excimer laser annealing (lambda = 308 nm) in the melting regime with different laser energy densities and single or multiple pulses. Arsenic is observed to diffuse similarly for different fluences with no out-diffusion and no formation of pile-up at the maximum melt depth. The diffusion profiles have been satisfactorily simulated by assuming two diffusivity states of As in the molten Ge and a non-equilibrium segregation at the maximum melt depth. The electrical activation is partial and decreases with increasing the chemical concentration with a saturation of the active concentration at 1 x 10(20) cm(-3), which represents a new record for the As-doped Ge system

Stability, bonding, and electronic properties of silicon and germanium arsenides

“…Arsenic has been used as a doping agent in silicon and germanium to produce n‐type semiconductors for several decades, and many studies have been done on this subject. Even quite recently, the doping issues of As impurities in silicon and germanium are still research topics indicating the importance of the SiAs and GeAs systems . The phase diagrams of the silicon–arsenic and germanium–arsenic systems showed two types of compounds, i.e., XAs and XAs 2 (X = Si, Ge) .…”

Electrical compensation via vacancy–donor complexes in arsenic-implanted and laser-annealed germanium

“…1), it is evident that the vacancy distribution extends markedly beyond the melt depth in each of the doped samples. This is rather a peculiar observation, as the SIMS profiles 15 show that the As concentration drops abruptly at depths exceeding the melted layer. Various implantation studies on Si and SiC have found the vacancy-type defects well beyond the projected range of the implanted ions, and it has often been suggested to be due to vacancies produced within the projected range diffusing deeper into the sample.…”

“…For a comprehensive description of the preparation and characterizations of the samples, the reader can refer to Ref. 15. In brief, secondary ion mass spectrometry (SIMS) and spreading resistance profiling revealed As activation no better than 50%, which motivated the present study.…”

“…26 In a study on 4H-SiC, it was shown, however, that ion channeling can have a substantial impact and potentially explains many of the observations attributed to vacancy migration. 27 Extrapolating the SIMS data 15 for the exponentially decaying channeling tail, it can be concluded that the As concentration falls slightly below 10 16 and 10 17 cm À3 at 200 nm for As1 and As2, respectively, dropping by roughly two orders of magnitude more at 300 nm. It seems unlikely that such low implant concentrations could account for the detectable amounts of V-type defects below the regrown layer.…”

Ge p-channel tunneling FETs with steep phosphorus profile source junctions

“…16,17) However, it is difficult to realize such source junctions in Ge p-channel TFETs (p-TFET) because of the low solid solubility limit and high diffusivity of n-type dopants in Ge. [19][20][21] Defect-free source junctions are also needed to suppress trap-assisted tunneling and generation-recombination processes, which increase the leakage current. 18) Ion implantation is a typical method of introducing impurities into semiconductor materials.…”