Photoresponses of the back-side illuminated GaAs photoconductive semiconductor switches in the linear mode

•Photoresponses of the back-side illuminated photoconductive semiconductor switches are studied.•The back-side-illuminated PCSS enjoys the better performance than that of the front-side-illuminated one.•The laser beam centered near the cathode yields the slowly-decaying output pulse waveform. Photoresponses of the back-side illuminated photoconductive semiconductor switches (PCSSs) in the linear mode are studied. It has been found that the back-side-illuminated PCSS enjoys the better performance than that of the front-side-illuminated one. Photogeneration of electron-hole pairs beneath the contacts under the back-side illumination condition significantly reduces the resistance of the PCSS leading to the higher output pulse amplitude up to 4.6 times. Impact of the beam center position on the output waveform is also investigated for both the illumination cases. The laser beam centered near the cathode yields the slowly-decaying output pulse waveform. On the other hand, the rapidly-decaying waveform is observed with the beam centered near the anode.