Nanoscale n++-p junction formation in GeOI probed by tip-enhanced Raman spectroscopy and conductive atomic force microscopy

Abstract

Ge-on-Si and Ge-on-insulator (GeOI) are the most promising materials for the next-generation nanoelectronics that can be fully integrated with silicon technology. To this day, the fabrication of Ge-based transistors with a n-type channel doping above 5 × 10 19 cm −3 remains challenging. Here, we report on n-type doping of Ge beyond the equilibrium solubility limit (n e ≈ 6 × 10 20 cm −3 ) together with a nanoscale technique to inspect the dopant distribution in n ++ -p junctions in GeOI. The n ++ layer in Ge is realized by P + ion implantation followed by millisecond-flashlamp annealing. The electron concentration is found to be three times higher than the equilibrium solid solubility limit of P in Ge determined at 800°C. The millisecond-flashlamp annealing process is used for the electrical activation of the implanted P dopant and to fully suppress its diffusion. The study of the P activation and distribution in implanted GeOI relies on the combination of Raman spectroscopy, conductive atomic force microscopy, and secondary ion mass spectrometry. The linear dependence between the Fano asymmetry parameter q and the active carrier concentration makes Raman spectroscopy a powerful tool to study the electrical properties of semiconductors. We also demonstrate the high electrical activation efficiency together with the formation of ohmic contacts through Ni germanidation via a single-step flashlamp annealing process.

Chlorine doping of MoSe2 flakes by ion implantation

“…6). 52 In heavily doped semiconductors, the Fano parameter  is determined by the dopant concentration, while the Fano asymmetry parameter q is proportional to the electrically active dopants; 53 in our case Cl. Moreover, the absolute value of q decreases with increased carrier concentration, while  increases.…”

Electron Concentration Limit in Ge Doped by Ion Implantation and Flash Lamp Annealing

“…Unfortunately, at high temperature, a strong diffusion of dopants takes place, which widens the depth distribution of donors. According to the literature, the maximum concentration of electrons in Ge increases with decreasing thickness of the doping layer, regardless of doping techniques [11]. For example, using the MBE method and delta doping, if the thickness of the doping layer is in the range of a few nm, the effective concentration of the carriers can be as high as 2 × 10 20 cm −3 [12].…”

“…For example, using the MBE method and delta doping, if the thickness of the doping layer is in the range of a few nm, the effective concentration of the carriers can be as high as 2 × 10 20 cm −3 [12]. P-implanted Ge shows the highest carrier concentration of approximately 6 × 10 20 cm −3 for a layer thickness of around 40 nm [11]. Kujala et al examined the deactivation of donors in strongly doped Ge using positron annihilation spectroscopy [13].…”