Electropassivation of silicon and bulk lifetime determination with dry polymer contact

Abstract

A new method for the determination of the bulk lifetime of minority carriers in silicon is presented. By applying a dry polymer (poly-epichlorhydrin-co-ethyleneoxide-co-allyl-glycylether with iodide/iodine) to silicon and exerting a negative potential to the silicon, an increase of the lifetime of photogenerated charge carriers (from 25 to 92 µs), measured by microwave conductivity techniques, is observed. This effect is caused by the electric field, which pulls minority carriers into the interior of the silicon wafer so that surface recombination can only continue on the back contact of the wafer. It is shown how, from this electropassivation effect, the bulk lifetime of silicon (0.81 ms in this case) and the effective diffusion constant can be obtained. Space-resolved images of minority carrier lifetimes show that it is difficult to get a homogeneous polymer-silicon contact at the whole wafer surface. Minority carrier lifetime against potential curves show that only polished silicon surfaces can be perfectly electropassivated. The procedure presented has potential for development as a technique for wafer characterization.

Fourier single-pixel imaging in the terahertz regime

“…For I 0 = 350 mW and A = 16 mm 2 , the calculated carrier density of the HRS is found to be n = 6.05×10 16 cm −3 , and the calculated carrier lifetime is τ = 23.3 µs. We note that this carrier lifetime is comparable to the measured value (∼ 25 µs) reported in the literature [29,30]. Similarly, for the GOS, we find that the calculated carrier density is n = 3.59 × 10 17 cm −3 , and the calculated carrier lifetime is τ = 138.1 µs, which is about six times of that for the HRS substrate.…”

Terahertz single pixel imaging with an optically controlled dynamic spatial light modulator

“…where I 0 is average power, R is the reflectivity of Si at the pump wavelength,hω is the photon energy, τ = 25 μs is the carrier lifetime [32], A is the area of the laser excitation, and d is the penetration depth. At THz frequencies the photodoped charges correspond to a large increase in the absorption coefficient as a function of I 0 , allowing for strong attenuation of incident THz electromagnetic waves.…”

Comparison of dielectric surface passivation of monocrystalline and multicrystalline silicon

“…In order to determine S, the contributions of both S and τb to the effective lifetime (τeff) must be separated. Every known method for suppressing S to determine τb has its drawbacks, as described in [7]. Additionally, we recently showed [8] that while an iodine/methanol solution [9] reliably passivates the monocrystalline silicon surface more effectively than the dielectrics under investigation, the string ribbon silicon surface is often less effectively passivated by the iodine/methanol solution than the dielectrics.…”