3D interconnects for III-V semiconductor heterostructures for miniaturized power devices

Three-dimensional (3D) interconnects increase chip power density and enable miniaturization. Photonic chips require new processes to enable transitioning to 3D interconnects. We fabricate 3D interconnects on a multijunction solar cell, leveraging processes such as III-V heterostructure plasma etching, gold electrodeposition, and chemical-mechanical polishing to integrate through substrate vias to the heterostructure. Wafer bonding is used to handle 20-μm-thin III-V films. The strategy enables us to demonstrate photonic power devices having areas 3 orders of magnitude smaller compared to standard chips. The design also yields a small shading factor below 3%. Compared to miniaturized photonic power devices with two-dimensional connections, 3D interconnects achieve a 6-fold increase in wafer area use. These improvements will enhance the power yield per wafer while unlocking high-density and miniaturized devices for applications such as power over fiber, the internet of things, and microconcentrator photovoltaics.