Structural Design and Experiment of Narrow-Band Response GaAlAs Photocathodes

To obtain the peak response at 532 nm, narrow-band response GaAlAs photocathodes with two GaAlAs active layers of different aluminum compositions are designed in consideration of the maximum absorptivity and quantum efficiency. The transmission-mode and the corresponding reflective-mode photocathodes are grown by metalorganic chemical vapor deposition. The results indicate that the peak response and the cut-off wavelength occur at 532 nm for the two kinds of photocathodes respectively. The response of the reflection-mode photocathode is an order of magnitude higher than that of the transmission-mode photocathode, whereas the better growth quality and the thicker second GaAlAs active layer can improve the transmission-mode response.