The determination of high-density carrier plasma parameters in epitaxial layers, semi-insulating and heavily doped crystals of 4H-SiC by a picosecond four-wave mixing technique

Abstract

We applied a picosecond four-wave mixing technique for measurements of carrier lifetimes and diffusion coefficients in highly excited epitaxial layers, semi-insulating and heavily doped 4H-SiC substrates. Optical carrier injection at two different wavelengths (266 and 355 nm) allowed us to vary the depth of the excited region from 1-2 µm to 50 µm, and thus determine photoelectric parameters of carrier plasma in the density range from 2 × 10 16 to 10 19 cm −3 . Strong dependence of carrier lifetime and mobility on carrier density was found in the epitaxial layers. The origin of fast decay components, not resolved previously by photoluminescence and free-carrier absorption techniques in SiC, was attributed to nonlinear carrier recombination. Numerical modelling provided a value of bimolecular recombination coefficient equal to B = (2-4) × 10 −11 cm 3 s −1 and verified a surface recombination velocity S = 4 × 10 4 cm s −1 . In heavily doped crystals, nonlinear carrier recombination reduced the carrier lifetime down to 1.1 ns, while in semi-insulating ones a lifetime of 1.5-2.5 ns was measured. Temperature dependences of four-wave mixing provided monopolar carrier mobility in heavily doped and bipolar one in semi-insulating crystals, and revealed the contribution of ionized impurity and phonon scattering mechanisms.

Nonlinear carrier recombination and transport features in highly excited InN layer

“…To our knowledge, the time-resolved picosecond four-wave mixing (FWM), or transient grating technique has been proved as an excellent tool for studies of non-equilibrium carrier recombination and diffusion processes in wide excitation and temperature range of differently grown GaN layers [9][10][11], SiC [12], and diamond crystals [13]. Recently, it revealed contribution of extended defects to carrier recombination in In-rich InN alloys [14].…”

Comparative Studies of Carrier Dynamics in 3C-SiC Layers Grown on Si and 4H-SiC Substrates

“…These included light diffraction on transient free carrier grating (LITG) 16,17 and free carrier absorption (FCA). 18,19 Measurements were made over a wide range of excess carrier density, DN 0 = 10 16 cm À3 to 10 19 cm À3 , and temperature, T = 80 K to 800 K. The carriers were excited by a frequency-tripled Nd:YLF laser at 351 nm.…”

“…Taking into account carrier diffusion and recombination, the carrier density and its spatial distribution were numerically calculated. 17,19 This procedure was based on modeling of the spatial redistribution of the injected carriers DN(z, t) in an epitaxial layer of thickness d by the balance Eq. 1 using the standard boundary conditions and the bipolar diffusion coefficient D a 17 :…”

A diffraction-based technique for determination of interband absorption coefficients in bulk 3C-, 4H- and 6H-SiC crystals

“…A deeper understanding of these processes in high-density carrier plasma can be obtained by applying time-resolved optical techniques, which allow the injection of an excess carriers by a short laser pulse and subsequent monitoring of the recombination and diffusion processes [1][2][3][4][5][6][7]. Therefore knowledge of absorption coefficent at commonly used laser wavelengths is an important issue for more precise determination of injected carrier density profile and related plasma parameters in SiC, e.g.…”