Growth and characterization of a delta-function doping layer in Si

Abstract

We present a procedure whereby a sheet of donor atoms is incorporated in (100) Si during molecular beam epitaxial growth, Analysis by secondary ion mass spectroscopy and transmission electron microscopy shows that the width of such 8-function doping layers is only a few lattice planes. Tunneling spectroscopy and transport measurements give evidence for quantum confinement of the electronic charge in the layer and thus confirm the narrow width.For a number of Si device applications an extremely sharp and high density doping profile is required. In principle such a sharply defined doping layer can be achieved with molecular beam epitaxial (MBE) growth ofSi. The problem is that for Sb or Ga densities in the 10 20 em -3 range there are significant surface segregation and a low rate of incorporation into the growing Si crystal, At the typical growth temperature of -700 °C the dopants are carried along the surface of the growing crystal. The doping profile is significantly broadened. 1To overcome this difficulty two procedures have been reported in the literature. In Ref 2 the co-evaporation of a layer of Si and dopant at room temperature followed by solid phase epitaxy has been employed. Reference 3 introduces secondary ion implantation, whereby a negative potential ( -500 V) is applied to the substrate and the dopant is incorporated by knock-on from Si ions. Doping spikes of _10 19 em <I Sb with width 2-3 nrn in an n-type eND;::::: 10 10 em - 3) background have been achieved. 4 ,5 We present here a growth method related to Ref. 2 but designed to achieve the sharpest possible confinement of the dopant. The basic idea is to first evaporate the Sb dopant to the desired submonolayer coverage and then cover it with a thin amorphous Si layer all at room temperature, The growth procedure for the present samples commences with a buffer layer of 0.4 pill of Si, grown at a rate of 0.5 nm/s at

Thomas-Fermi approximation inp-type δ-doped quantum wells of GaAs and Si

“…Work on ␦-doped structures was initially on n-type structures, and has allowed one to study the subband spectra and mobilities of these systems through electrical and optical measurements. [1][2][3][4] p-type ␦-doped GaAs quantum wells can be made with Be, Si-acceptor, and C layers. [5][6][7][8] They are suitable systems for the study of the physics at extremely high carrier densities, and for potential technological applications (␦-FET, 2,9,10 ALD-FET, 11 etc.͒.…”

B/Si(100) surface: Atomic structure and epitaxial Si overgrowth

“…[1][2][3][4][5][6][7] A new challenge for the delta-doping technique is the fabrication of delta-doped layers with ordered two-dimensional structures of the dopants ͑ordered delta doping͒. Such delta-doped layers have been produced successfully in Si using molecular beam epitaxy ͑MBE͒ and MBE-related solid phase epitaxy ͑SPE͒.…”

Electronic states in n-type GaAs delta-doped quantum wells under hydrostatic pressure

“…The localization of ionized impurities in a very thin layer gives rise to a very intense electric field which -in turns-causes a bending of the energy bands and the occurrence of a particular V-shaped potential. Work on δ-doped structures was primarily in n-type, on Si and III-V semiconducting materials (see, for instance, [1][2][3][4][5][6][7][8]). However, there is also an early report on this kind of system grown on Al x Ga 1−x As alloy [9].…”