Toward High-Efficiency Scalable GaAs and GaAs x P 1-X Photoelectrodes Grown Via Vapor Transport from a Solid Source

GaAs and related III-V semiconductors are attractive materials for high-efficiency water-splitting photoelectrodes, but their implementation is limited in part by the high cost of metal-organic chemical vapor deposition, which employs toxic and pyrophoric gas-phase precursors. We report the study of GaAs and GaAs x P 1-x grown by close-space vapor transport (CSVT), which uses solid GaAs as a source and water vapor as a transport agent as an alternative low-cost technique for depositing GaAs films and microstructures. The free carrier type and density (10 16 – 10 19 cm -3 ) in the films was adjusted by addition of Te or Zn powder to the GaAs source powder. The electronic properties of films grown under a variety of conditions are evaluated and correlated with the film structure and impurity content. We show using photoelectrochemical and electron beam-induced current analyses that the minority carrier diffusion lengths of the n - and p -GaAs epitaxial films reached 2-3 µm and 5-7 µm, respectively. Hall mobilities approach those achieved for GaAs grown by metal organic chemical vapor deposition, 500 - 4,000 cm 2 V -1 s -1 for n -GaAs and 50-240 cm 2 V -1 s -1 for p- GaAs depending on carrier concentration. Related efforts to control carrier collection through surface texture as well as the growth of GaAs on Si as an inexpensive high-efficiency tandem photoelectrode will also be discussed. Ritenour, A. J.; Boucher, J. W.; DeLancey, R.; Greenaway, A. L.; Aloni, S.; Boettcher, S. W. Doping and Electronic Properties of GaAs Grown by Close-Spaced Vapor Transport from Powder Sources for Scalable III-V Photovoltaics. Energy Environ. Sci. Accepted, 2014 . Ritenour, A. J.; Levinrad, S.; Bradley, C.; Cramer, R. C.; Boettcher, S. W. Electrochemical Nanostructuring of n-GaAs Photoanodes. ACS Nano , 2013 , 7 (8), 6840–6849. Ritenour, A. J.; Cramer, R. C.; Levinrad, S.; Boettcher, S. W. Efficient n-GaAs Photoelectrodes Grown by Close-Spaced Vapor Transport from a Solid Source. ACS Appl. Mater. Interfaces 2012 , 4 , 69-73.