D. A. Kudryashov

Si doped GaP layers grown on Si wafers by low temperature PE-ALD

Low-temperature plasma enhanced atomic layer deposition (PE-ALD) was successfully used to grow silicon (Si) doped amorphous and microcrystalline gallium phosphide (GaP) layers onto p-type Si wafers for the fabrication of n-GaP/p-Si heterojunction solar cells. PE-ALD was realized at 380 °C with continuous H2 plasma discharge and the alternate use of phosphine and trimethylgallium as sources of P and Ga atoms, respectively. The layers were doped with silicon thanks to silane (SiH4) diluted in H2 that was introduced as a separated step. High SiH4 dilution in H2 (0.1%) allows us to deposit stoichiometric GaP layers. Hall measurements performed on the GaP:Si/p-Si structures reveal the presence of an n-type layer with a sheet electron density of 6–10 × 1013 cm−2 and an electron mobility of 13–25 cm2 V−1 s−1 at 300 K. This is associated with the formation of a strong inversion layer in the p-Si substrate due to strong band bending at the GaP/Si interface. GaP:Si/p-Si heterostructures exhibit a clear photovoltaic effect, with the performance being currently limited by the poor quality of the p-Si wafers and reflection losses at the GaP surface. This opens interesting perspectives for Si doped GaP deposited by PE-ALD for the fabrication of p-Si based heterojunction solar cells.

The temperature dependence of the electrical conductivity in Cu2O thin films grown by magnetron sputtering

The temperature dependence of the electrical conductivity in Cu2O thin films grown by magnetron sputtering at room temperature under different rf-power was investigated. Calculated activation energy of the conductivity for copper oxide (I) films linearly increases with increase in sputtering power reflecting an increasing in concentration of gap states.

Defect properties of InGaAsN layers grown as sub-monolayer digital alloys by molecular beam epitaxy

The defect properties of InGaAsN dilute nitrides grown as sub-monolayer digital alloys (SDAs) by molecular beam epitaxy for photovoltaic application were studied by space charge capacitance spectroscopy. Alloys of i-InGaAsN (Eg = 1.03 eV) were lattice-matched grown on GaAs wafers as a superlattice of InAs/GaAsN with one monolayer of InAs (<0.5 nm) between wide GaAsN (7–12 nm) layers as active layers in single-junction solar cells. Low p-type background doping was demonstrated at room temperature in samples with InGaAsN layers 900 nm and 1200 nm thick (less 1 × 1015 cm−3). According to admittance spectroscopy and deep-level transient spectroscopy measurements, the SDA approach leads to defect-free growth up to a thickness of 900 nm. An increase in thickness to 1200 nm leads to the formation of non-radiative recombination centers with an activation energy of 0.5 eV (NT = 8.4 × 1014 cm−3) and a shallow defect level at 0.20 eV. The last one leads to the appearance of additional doping, but its concentration i...

Photoluminescence observation from zinc oxide formed by magnetron sputtering at room temperature

The photoluminescence (PL) of ZnO thin films grown by magnetron sputtering at room temperature has been observed. The PL spectra were measured using an instrument from Accent Optical Technologies with a solid state UV laser (λ = 266 nm) as the pumping source and at the temperature of 300 K. Samples grown at sputtering power of 100-200 W show a strong photoluminescence (PL) at wavelength of 377 nm and its intensity shows non-linear dependence with magnetron power. At values of sputtering power less then 100 W PL signal was not observed. A correlation between PL, XRD intensity and ZnO grain size was shown.

Indium tin oxide films grown at room temperature by RF-magnetron sputtering in oxygen-free environment

Indium Tin Oxide (ITO) thin films were grown at room temperature (RT) in oxygen-free environment by rf-magnetron sputtering on glass and Si(100)-substrates. The effects of argon pressure, sputtering power and film thickness on the electrical and optical properties of ITO films were investigated. For a 100 nm thick ITO films grown at RT in argon pressure 1.95∙10-3 mbar and sputtering power of 50 W, the transmittance was near 90% at 500 nm and resistivity was 5.4∙10-4 Ohm∙cm. It has been shown that the sputtering power plays an important role in electric properties of ITO films. SEM images of these samples show smooth surface with sharp substrate/ITO interface.