Ambipolar diffusion coefficient in molecular-beam-epitaxy-grown silicon layers

Abstract

The noncontact transient grating technique under constant electron-hole pumping to the density 4×1019 cm−3 was used to characterize the ambipolar diffusion coefficient Da in Si:Al, Si:In, and Si:Sb molecular-beam-epitaxy-grown layers. Da was found to be almost constant at a value of ≊8 cm2/s up to an equilibrium carrier density of 2×1019 cm−3 in the layer and was independent of the doping type. At higher doping density, evidence for a sharp increase in Da was observed. For example, Da increased to a value of 20 cm2/s at a doping density of about 1020 cm−3. The Da behavior is in reasonable agreement with results of the high-density ambipolar diffusion theory of Young and van Driel and is incompatible with majority-carriers diffusion coefficients according to the formula Da = 2DnDp/(Dn + Dp). An explanation for this behavior is given.

Photoexcited carrier diffusion near a Si(111) surface: Non-negligible consequence of carrier-carrier scattering

“…2 are the bulk ambipolar diffusivities previously measured with the transmission transient grating technique [17][18][19][20][21] at both lower and higher carrier density. The measured ambipolar diffusivity as a function of carrier density over a six order-of-magnitude range clearly displays a dip with a minimum value at Nϳ1ϫ10 19 cm Ϫ3 .…”

Hole transport and carrier lifetime in InN epilayers

“…11 The presence of a high unintentional n-type doping level in InN, however, makes this technique impractical for measuring the hole mobility as well as the hole diffusion length. [13][14][15][16] In this method, the simultaneous determination of hole mobility and carrier lifetime of InN is possible. 12 All of these techniques generally have relatively extensive sample preparation procedures, and some of these methods have very limited applicability.…”

“…When assuming a monomolecular recombination, the decay rate G is given by [13][14][15][16] When assuming a monomolecular recombination, the decay rate G is given by [13][14][15][16] …”

Measuring photocarrier diffusivity near a Si(111) surface by reflective two-color transient grating scattering

“…However, even for the well-studied silicon crystal, [1][2][3][4][5][6] the uncertainty in the measured carrier diffusivity is still appreciable. Furthermore, in recent studies of light induced chemical processes on surfaces, the intensity of the light used often induces a high carrier density in the substrate.…”

“…2,3,[5][6][7][8] In most cases, the transient grating experiments have been done in the transmission diffraction geometry. Even though it is technically more challenging, the transient grating experiments can be done in the reflection diffraction geometry for probing dynamics near a surface.…”