Light Trapping in Conformal CuO/Si Pyramids Heterojunction for Self-Powered Broadband Photodetection

In this letter, we report a conformal CuO/Si micropyramids heterojunction photodetector fabricated by RF reactive magnetron sputtering CuO nanofilm onto the dense and random Si micropyramids. The device presents a prominent photovoltaic effect over the broad wavelength range (300-1300 nm), which enables efficient self-powered broadband photodetection, giving a peak responsivity of 279 mA/W and specific detectivity of $1.18\times10$ 11 Jones at zero bias upon 810 nm illumination at light intensity of $5.9~\mu \text{W}$ /cm2. Compared to its planar Si counterpart, the conformal CuO/Si pyramids heterojunction photodetector shows a significantly enhanced photoresponse over the broadband region. According to the theoretical simulation of photon absorption in Si pyramid structures, this should be ascribed to the pronounced light trapping effect of the pyramid structures. The light-matter interaction in the heterojunction was accordingly enhanced, leading to the improved photoresponse. This work is well compatible with the current complementary metal-oxide semiconductor (CMOS) technology and provides a facile and effective strategy for the on-chip high performance photodetection.