Complementary optoelectronic interaction of n+-Si/p-Ge heterojunctions fabricated via transfer printing toward broadband photodetectors

Heterojunctions have been recognized as promising candidates for the fabrication of broadband photodetectors. However, currently demonstrated heterojunctions suffer from one or more disadvantages in limited light absorption, incompatible fabrication with the current semiconductor technology, and/or abundant interface defects induced by lattice/thermal mismatches. In this work, we use traditional elemental semiconducting materials to construct n+-Si/p-Ge heterojunctions by the transfer printing method, which are further explored as broadband photodetectors. Key advantages are in capabilities for avoiding the defects induced by the lattice and thermal expansion mismatches, and for detecting the illuminated light with the wavelength covering the visible-near-infrared range. Controlling the layer stacking order of the heterojunction could enable a complementary optoelectronic interaction between Si and Ge, which facilitates the effective generation of electron–hole pairs in a wide spectrum of light illumination. This work adds to the portfolio of material strategies and fabrication approaches in high-performance broadband photodetectors.