Lifetime and diffusion length of photogenerated minority carriers in single-crystalline n-type β-FeSi2 bulk

Abstract

We have evaluated the lifetime and diffusion length of photogenerated minority carriers ͑holes͒ in single-crystalline n-type ␤-FeSi 2 bulk grown by chemical vapor transport. The diffusion length measured by optical-beam-induced current agreed well with that measured by electron-beam-induced current, that is, 51 and 38 m, respectively, for samples annealed at 800°C for 8 h. The decay curve of photoconductivity obtained by 1.31 and 1.55 m light pulses was well fitted by assuming a carrier lifetime of approximately a few microseconds. The mobility of photogenerated minority carriers was estimated to be approximately 200-360 cm 2 / V s from the measured lifetime and diffusion length.

Improved photoresponsivity of semiconducting BaSi2 epitaxial films grown on a tunnel junction for thin-film solar cells

“…Photocurrents were observed for photon energies greater than 1.25 eV and increased sharply for photon energies greater than 1.3 eV, reaching a maximum photoresponsivity of 0.37 A/W at 1.55 eV when the bias voltage was 2.0 V. These values are the highest ever reported for semiconducting silicides and are more than three times higher than the value of 0.1 A/W at 0.98 eV obtained for a bulk n-type b-FeSi 2 single crystal. 25 Compared with the result for sample B, the photoresponsivity is increased by more than 30 times. This is attributed to suppression of the thermal diffusion of Sb atoms in the BaSi 2 layers due to the presence of the c-Si layer grown by SPE, and the resulting heavier Sb concentration in the n þ -BaSi 2 layer enables the formation of the high-quality TJ in sample A.…”

Minority-carrier diffusion length, minority-carrier lifetime, and photoresponsivity of β-FeSi2 layers grown by molecular-beam epitaxy

“…An electron-beam-induced current (EBIC) technique revealed that the minority-carrier diffusion length in single crystalline n-type b-FeSi 2 is approximately 50 lm. 10 In contrast, the minority-carrier diffusion length of b-FeSi 2 films has not been reported. The lower photoresponsivity (and thus shorter minority-carrier diffusion length) in b-FeSi 2 films is probably due to defects at the grain boundaries of b-FeSi 2 epitaxial variants on Si substrates [15][16][17] and high residual carrier (hole) concentrations reaching approximately 10 19 cm À3 at room temperature (RT).…”

“…[3][4][5][6][7][8] In particular, a photoresponsivity of over 100 mA/W for 1.31 lm light for n-type b-FeSi 2 single crystals has renewed interest in this material. 9,10 The photoresponsivity obtained for b-FeSi 2 thin films has been increasing each year. [11][12][13][14] However, the highest photoresponsivity obtained so far for b-FeSi 2 thin films (3.3 mA/W at 1.31 lm) 13 is still more than one order of magnitude smaller than that for n-type b-FeSi 2 single crystals.…”

Synthesis and characterization of β-phase iron silicide nano-particles by chemical reduction

“…While most of the silicides have good metallic properties there are very few having attractive semiconducting properties. The ␤-phase of iron silicide (␤-FeSi 2 ) is one of the candidates that has the best potential for Si based photovoltaic and optoelectronic applications due to its (i) direct band gap (0.85-0.87 eV) with a wide range of absorption spectrum starting from infrared to visible region [1,2], (ii) higher optical absorption coefficient (>10 5 cm −1 at 1 eV photon energy) compared to that of silicon (of the order of 10 2 cm −1 at 1 eV [2,3]), (iii) long enough hole and electron diffusion length for a specific doping concentration [5,6] and (iv) it can also be grown epitaxially on Si substrate (lattice mismatch only ∼2-5.5%) [6,7]. In addition, it has good physical and chemical stability (e.g.…”

“…There has been increasing research on metal silicides during last few years [1][2][3][4][5] for its application in Schottky barriers, ohmic contacts, interface diffusion barriers and photovoltaics. While most of the silicides have good metallic properties there are very few having attractive semiconducting properties.…”