Epitaxial layers of n-GaAs1-xPx (0 < x < 1) have been studied as photoelectrodes and as Au Schottky junctions. We observe increases in open-circuit voltage, Voc, with increases in P content for n-GaAs1-xPx (x ≤ 0.4) and decreases in Voc for ≤ 0.6. Under 88 mW/cm2 of ELH-type.(3350 K color temperature with a dichroic rear reflector) tungsten-halogen irradiation, we observe that n-GaAs0.72P0.28 anodes exhibit a Voc of 0.95-0.99 V, short-circuit currents of 15-17 mA/cm2, and energy conversion efficiencies of 13.0 ± 1.0%. Irradiation at 632.8-nm yields monochromatic conversion efficiencies of greater than 30%, and solar irradiation (85-100 mW/cm2) yields efficiencies of 11.0 ± 1.0% in 1.0 M KOH/1.0 M Se2-/0.-01 M Se22- solutions. The n-GaAs0.72P0.28 anodes exhibit stable photocurrent for passage of over 3000 C/cm2 at AM1 photocurrent densities. Ru(H2O)63+ ions are effective in improving photocurrent-voltage characteristics for H-GaAs1-xPx (0 ≤ x < 1) anodes but have no effect for n-GaP, indicating chemical interactions of the Ru ion with As or As oxide sites at the semiconductor/liquid junction. Direct comparison of Voc for n-GaAs1-xPx/Au junctions with n-GaAs1-xPx/Se2- barriers indicates that liquid junctions have higher Voc values than some Schottky barriers and that pinning of the Fermi level by intrinsic surface states may not play a dominant role in determining interface parameters for these junctions.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry