Xuanzhang Li

Porous silicon-based photodetectors have attracted more researches due to their high luminous efficiency, good stability and low cost. In this paper, a PbS quantum dots/porous silicon hybrid structure has been fabricated. The PbS quantum dots (QDs) partly infiltrated into the porous silicon (PSi) layer and partly deposited on its surface, which could increase the absorption of near-infrared wavelength range and extend the light absorption in silicon for wavelengths longer than 1100 nm. After that, A metal-semiconductor-metal (MSM) device is fabricated and its response spectrum could extend to the 1200 nm at -3 V. As a silicon-based photodetector (PD), one can envision its role for operation from visible light to short-wavelength infrared range.

Suppression pre-breakdown in planar separated absorption, grading, charge and multiplication (SAGCM) avalanche photodiodes (APDs) with the help of Floating Guard Ring (FGR) is still a research hotspot. In this paper, a lattice-matched InP/InGaAs-based SAGCM structure is grown by Metal-Organic Chemical Vapor Deposition and thus the planar 50 μm photosensitive area APDs with different FGR structures are fabricated using zinc diffusion process. The effects of the different lengths of FGR (4 μm, 8 μm, 12 μm, 16 μm), and the different distances between FGR and the Zn diffused p+ region (4 μm, 6 μm, 8 μm, 10 μm) on the optoelectrical characteristics are deeply studied. The results from optical microscope, scanning electron microscope and current-voltage curves reveal that there is an optimal length and distance for the punch-through and breakdown voltage. Furthermore, the nA-level dark current, gain ( M ) of up to 10 at breakdown voltage, responsibility as high as 9.01 A/W at M = 10 and quantum efficiency equaling to 72% are also tested and calculated, proving the good performance of our devices. The optimized FGR parameters and related structure are expected to be helpful for obtaining high-performance, small-size InP/InGaAs-based APDs.