High photocurrent and high frequency response of light-addressable potentiometrie sensor with thin Si substrate and surface roughness

For two dimensional (2D) chemical images by light-addressable potentiometric sensor (LAPS), high photocurrent obtained in high ac frequency is the most critical criterion to have an acceptable signal-to-noise ratio in a very short time for a pixel. A simple KOH etch can be used to decrease the thickness of silicon substrate for high photocurrent. In the meantime, higher surface roughness in both sides could be achieved by etching flat surface, which is also benefit for high photocurrent and pH sensitivity for rough back and front side, respectively. With this 175μm-thick Si substrate, operating at 20 kHz could be used to collect 2D chemical images easily.