Novel reflection mode and transmission mode GaAs (grown by metal organic chemical vapour deposition) photocathodes with the structures (GaAs-Na3Sb-Cs)-O-Cs, (GaAs-K3Sb-Cs)-O-Cs, (GaAs-Cs3Sb-Cs)-O-Cs and (GaAs-Na2KSb-Cs)-O-Cs were fabricated. For reflection mode (GaAs-Na3Sb-Cs)-O-Cs, (GaAs-K3Sb-Cs)-O-Cs, (GaAs-Cs3Sb-Cs)-O-Cs, (GaAs-Na2KSb-Cs)-O-Cs, and transmission mode (GaAs-Na2KSb-Cs)-O-Cs compound photocathodes, the measured maximum photosensitivities were respectively 100, 200, 60, 450, and 600 mu A lm(-1), the measured minimum work functions were respectively 1.35, 1.4, 1.25, 1.05 and 1.3 eV, the decay rates of photosensitivity were respectively about 12, 10, 15, 9 and 8 times slower than that of conventional GaAs photocathodes. In this paper, surface atomic models and energy band diagrams of the new compound GaAs photocathodes are analysed briefly.