Micropatterned Indium–Tin Oxide Grid Electrode for Vertical, Optoelectronic Field-Effect Transistors

Vertical field-effect transistors (VFETs) are promising for optoelectronic applications due to their low power consumption and vertical integration capability. For functional VFETs, porous source electrodes with nanoscale porosity have been required. However, reported patterning methods resulted in random pore distributions, and hence, control of the nanoporosity was challenging. Here, we report fabrications of an indium–tin oxide (ITO) grid by photolithography and its feasibility for integrated optoelectronic VFET applications. In spite of the micrometer-scale grid feature size, the resulting optoelectronic VFETs such as vertical light-emitting transistor and vertical infrared phototransistor exhibited comparable device performances as the reported VFETs with nanoscale porous electrodes. This is due to the highly ordered pore array on the ITO grid enabled by photolithography.