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.
Si doped GaP layers grown on Si wafers by low temperature PE-ALD
A. S. Gudovskikh, A. V. Uvarov, I. A. Morozov, A. I. Baranov, D. A. Kudryashov, E. V. Nikitina, A. A. Bukatin, K. S. Zelentsov, I. S. Mukhin, A. Levtchenko, S. Le Gall, J.-P. Kleider; Si doped GaP layers grown on Si wafers by low temperature PE-ALD. J. Renewable Sustainable Energy 1 March 2018; 10 (2): 021001. https://doi.org/10.1063/1.5000256
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