Investigations of the Electrical Properties of Porous Silicon

Abstract

We report capacitance and current-voltage measurements of porous silicon in contact with sputter-deposited aluminum. Three different substrates: 30-50 ~-cm boron-doped (p--type), 0.01-0.03 t~-cm boron-doped (p+-type), and 0.003-0.005 gt-cm phosphorus-doped (n § silicon, are used as starting material. Porous silicon formed from p--and p%type substrates exhibits full-and partial-carrier depletion, respectively. The electric field, potential distribution, and capacitance for full depletion are derived and shown to compare qualitatively with measured capacitance as a function of porous layer thickness for p--type porous silicon. Impedance variation with porous layer thickness was used to determine the resistivity of p--type porous silicon as 1.6 • 107 gt-cm. A three-dimen~ional space-charge region accounting for the observed partial depletion in p+-type porous silicon is described in detail. Capacitance with bias was used to measure the effective interface area of p+-type porous silicon. This reduced interface area can be explained in terms of a lateral depletion region surrounding each pore, with an average of 0.8 times the pore radius. Current-voltage measurements indicate a blocking contact between sputtered aluminum and both p--and p+-type porous silicon, in contrast to ohmic contacts between sputtered aluminum and nonporous p--and p+-type silicon. Capacitance-and current-voltage dependences of n § silicon indicate that in this material conversion to porous silicon has a relatively small effect.

Properties of bilayer contacts to porous silicon

“…As seen in Fig. 5, the PSi structure acts as a dielectric in a single capacitor with a value around 100 × 10 −12 F , which is in good accordance with other capacitive measurements in literature [29,30].…”

“…The rectifying behavior obtained has been previously identified in previous metal/PSi/Si structures [29,30,[32][33][34][35]. The symmetric behavior observed on the longitudinal mode is in fact in agreement with the Au/NiCr/PSi/NiCr/Au symmetric structure (metal/semiconductor-semiconductor/ metal).…”

Silicon Porosification: State of the Art

“…378 Whenever mesopores assume some defined geometric shape (which seems to be tied to low current densities), it consists of a connected octahedral. At higher current densities the mesopores are still growing in the (100) directions, but the geometric shape of the branches is lost; they appear "cloudy." 378…”

Observation of oxygen gas effect on porous silicon-based sensors

“…In these studies, the electrical and optical response of PS-based sensors have been investigated in the gas medium by performing conductance [8,9], capacitance [10,11] and photoluminescence (PL) measurements [12,13]. Both capacitive and ionic sensing modes in PS are described by Anderson et al [14].…”