Analysis of quantum efficiency improvement in spin-polarized photocathode

GaAs/GaAsP strain-compensatedsuperlattices(SLs) were developed for spin-polarizedphotocathode applications. High crystal quality was maintained with SL thicknesses up to 720  nm (90-pairs); however, the quantum efficiency (QE) did not increase linearly with the SL thickness but became saturated starting from an SL thickness of 192 nm (24-pairs). Time-resolvedphotoluminescencemeasurements revealed that thecarrier lifetime in the GaAs/GaAsP strain-compensated SL was as short as 20.5 ps at room temperature, which causes the elimination of photoexcited electrons before emission. A simulation based on adiffusion model was implemented to quantitatively evaluate the effect of thecarrier lifetime on the QE. The simulation results were in good agreement with the experimental results and demonstrate that acarrier lifetime of over 120 ps is required for a two-fold improvement of the QE.

Source: Journal of Applied Physics - October 24, 2016 Category: Physics Authors: Xiuguang Jin, Shunsuke Ohki, Tomoki Ishikawa, Atsushi Tackeuchi and Yosuke Honda Source Type: research