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Envisioning wide future relevance, work is reviewed here on the pure dopant deposition of boron (PureB), gallium (PureGa) and the combination of the two (PureGaB), as used in the fabrication of nanometer shallow p+n Si and/or Ge diodes. Focus is placed on the special properties that have put these diodes in a class apart: their ideal electrical behavior together with their electrical, optical and chemical robustness have lead to cutting-edge application as photodiodes for detecting low-penetration-depth beams, as for example in EUV lithography and low-energy electron SEM imaging. Of key importance is the effectively high Gummel number of the p+-region that provides low saturation currents despite the shallowness of the junctions. Based on experimental evidence it is proposed here that this is related to the formation of a practically complete surface coverage of acceptor states as an interface property of PureB on Si and PureGa on both Si and Ge.

Ion implantation induced damage accumulation is crucial to the simulation of silicon processing. We present a physically based damage accumulation model, implemented in a nonlattice atomistic kinetic Monte Carlo simulator, that can simulate a diverse range of interesting experimental observations. The model is able to reproduce the ion-mass dependent silicon amorphous-crystalline transition temperature of a range of ions from C to Xe, the amorphous layer thickness for a range of amorphizing implants, the superlinear increase in damage accumulation with dose, and the two-layered damage distribution observed along the path of a high-energy ion. In addition, this model is able to distinguish between dynamic annealing and post-cryogenic implantation annealing, whereby dynamic annealing is more effective in removing damage than post-cryogenic implantation annealing at the same temperature.

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A single-photon avalanche diode with high sensitivity in the ultraviolet (UV) wavelength range has been fabricated on Si using pure boron chemical vapor deposition to create both a nanometer-thin anode junction and a robust light entrance window. The device shows high sensitivity at the wavelengths of 330-370 nm when operated in the Geiger mode and good selectivity for UV light without applying a capping filter. The dark count rates can be as low as 5 Hz at room temperature for an active area of 7 µm 2 . An implicit guard ring, using an n-enhancement implantation in the central region of the diode, is applied instead of peripheral diffused p-type guard rings to achieve a high fill factor.Index Terms-Avalanche breakdown, boron, chemical vapor deposition (CVD), Geiger-mode avalanche photodiode, singlephoton avalanche diode (SPAD), ultrashallow junctions, ultraviolet (UV).