Evolution of structural and thermoelectric properties of indium-ion-implanted epitaxial GaAs

Abstract

We have examined the structural and thermoelectric properties of nanocomposites prepared by matrix-seeded growth, which consists of ion-beam-amorphization, followed by nanoscale recrystallization via annealing. We use a sputter-mask to increase the retained concentration of In+ ions in GaAs as a path towards the formation of nanoscale InAs crystals in an amorphous GaAs matrix. For the highest ion fluence, an enormous Seebeck coefficient of −12 mV/K is observed at 4 K. We discuss the temperature-dependence of the resistivity, Seebeck coefficient, and thermoelectric power factor in terms of the microstructure of the layers.

Time-resolved lateral spin-caloric transport of optically generated spin packets in n-GaAs

“…The maximum spin diffusion velocity |v s | ≈ 1000 cm/s of the LSCT measurements in Fig.3(a), which was measured at ξ H = 25 µm with dT /dx ≈ 0.5 K/µm, is obtained in our electric field-driven experiments at E x = 0.86 V/cm (see Fig. 4(a)), from which we estimate |S LSCT | ≈ 170 µV/K at T L = 6 K. These values are well below typical Seebeck coefficients |S| in GaAs exceeding 500µV/K at 10 K [40]. The small dependence of |S LSCT | on the lattice temperature T L in Fig.3(e) reaffirms that our LSCT is purely driven by a hot electron distribution without involvement of phonon drag effects.…”

“…3(a), which was measured at ξ H = 25 µm with dT /dx ≈ 0.5 K/µm, is obtained in our electric field-driven experiments at E x = 0.86 V/cm (see Fig. 4(a)), from which we estimate |S LSCT | ≈ 170 µV/K at T L = 6 K. These values are well below typical Seebeck coefficients |S| in GaAs exceeding 500µV/K at 10 K [40]. The small dependence of |S LSCT | on the lattice temperature T L in Fig.…”

“…The small dependence of |S LSCT | on the lattice temperature T L in figure 3(e) reaffirms that our LSCT is purely driven by a hot electron distribution without involvement of phonon drag effects. This is a unique feature of our experimental approach using local laser heating, in contrast to typical charge-based Seebeck effect measurements where phonon-drag results in a distinct extremum in the temperature dependent Seebeck coefficient at low temperature which we do not observe in our LSCT measurements [43,44].…”

Enhanced Photothermal Conversion in Vertically Oriented Gallium Arsenide Nanowire Arrays

“…The increased absorption and resonant waveguiding properties of nanowires are attracting ever increasing attention for a wide variety of applications including lasers, , solar cells, − structural color generation, − imagers, and sensors. − Specifically, vertically oriented nanowire arrays are known to have markedly increased optical absorption due to resonant coupling into optical modes . Nanowires have also been implicated as efficient thermoelectric materials. − Semiconductor nanowires are known to have thermal conductivities which are dominated by phonon processes, as opposed to electronic processes, which make them an attractive choice for thermoelectric devices. − For example, GaAs in its bulk form has a bulk thermal conductivity of 54 W m –1 K –1 , whereas GaAs nanowires have been reported to have thermal conductivity ranging from 8 to 36 W m –1 K –1 . Silicon nanowires have shown a 100-fold increase in ZT values over bulk silicon. − Computer simulations have also suggested that the thermal conductivity of nanowires can be further reduced by creating nanowires with rough surfaces .…”