Two-dimensional N-type Doping in Silicon with Antimony*

JPL-invented delta-doped and superlattice-doped ("2D-doped") silicon detectors offer high durability and high sensitivity to wavelengths spanning soft X-rays to near IR. Importantly, 2D-doped detectors offer a vast improvement in stability against damaging radiation. Device passivation by 2D-doping requires high dopant concentrations (~10¹⁴ cm^-2) with dopant layers confined to within a few nanometers of the surface. P-type doping with B from an effusion cell is relatively straightforward; B evaporates as an atomic beam, and the small boron atoms incorporate with the silicon crystal lattice. Conversely, n-type doping of silicon using Sb presents challenges, arising primarily from the tendency of antimony to segregate to the surface. However, at sufficiently low Si deposition rates epitaxial growth is achieved for finite thicknesses even at low temperatures. We previously reported on the low-temperature growth of Sb delta-doped silicon, demonstrating activated dose concentrations as high as 2×10¹⁴ cm^-2 and sharp dopant profiles (~35 Å FWHM). We have extended our capabilities to n-type superlattices. Electrical characterization and preliminary device measurements will be included.