We report an experimental demonstration of room-temperature InAlAs/InGaAs/InP planar two-dimensional to two-dimensional resonant tunneling-coupled transistors, in which the tunneling characteristics such as negative differential resistance and peak current are controlled by a surface Schottky gate similar to the state-of-the-art high-electron-mobility transistors (HEMT) with high gain. The tunneling peak voltage was modulated linearly with the Schottky gate voltage with a ratio of nearly unity. Functionality of the device can also be switched between HEMT and tunneling transistor mode. The fabrication process is fully compatible with conventional HEMT processes, offering a fully integrable and scalable tunneling transistor technology. (C) 2005 American Institute of Physics.