Researchers build vacuum tube that avoids gate leakage and works in logic circuits

A team from Shanghai Jiao Tong University and Shaoxing University has built a cathode-modulated vacuum/air-channel electron tube that eliminates gate leakage, a flaw that has blocked vacuum tubes from integrated circuits. The device, reported April 20, 2026, has already been demonstrated in amplifiers and NAND/NOR gates and could open a path to faster, more rugged chip-scale electronics. Why it matters: - The device removes gate leakage, the main barrier that has kept planar vacuum tubes out of integrated circuits. - If the approach scales, vacuum-tube chips could offer much higher speed than silicon transistors because electrons move through vacuum far faster than in solid-state devices. - The technology could matter most in high-frequency, radiation-heavy, and extreme-temperature environments such as aerospace, defense, and satellites. What happened: - Researchers from Shanghai Jiao Tong University and Shaoxing University reported a cathode-modulated vacuum/air-channel electron tube, or CMVET, in Microsystems & Nanoengineering on April 20, 2026. - The device was fabricated with standard IC-compatible processes on silicon-on-insulator wafers. - The team tested the CMVET in common-source amplifiers, differential amplifiers, cascade amplifiers, and NAND and NOR logic gates. - The authors say this is the first time a vacuum/air-channel electron tube has been shown inside functional integrated circuit blocks. The details: - The CMVET changes the operating principle of prior vacuum tubes by modulating electron concentration at the cathode instead of trying to control electrons mid-flight. - A back gate separated by an oxide layer bends the energy band of an ultrathin silicon cathode that is 45 nm thick. - Positive gate voltage increases field-emission current by pulling electrons toward the cathode surface. - Negative gate voltage reduces emission by repelling electrons. - Because emitted electrons are not intercepted by the gate, gate current stays below 10⁻¹¹ A. - The device runs at room temperature and atmospheric pressure. - Its output is non-saturating, meaning current continues to rise with anode voltage instead of flattening like a MOSFET. - Measurements show a switch current ratio of about 10⁴ and transconductance of about 23 μS. - The team reported amplifier gains up to 1.6. - The NAND gate produced high and low output levels of about 4.5 V and 1.9 V. - The NOR gate produced high and low output levels of about 4 V and 1.1 V. - The fabrication flow used standard oxidation, deposition, etching, and ion implantation. - The work was supported by the Smart Sensor Innovation Team Program of Shaoxing University. - The original paper is linked through the published DOI . Between the lines: - Previous planar vacuum-electron designs failed because gate control caused electrons to strike the gate, creating unavoidable leakage. - By shifting control to the cathode, the new design sidesteps the core weakness that made earlier attempts impractical for circuits. - The non-saturating current response is a real design tradeoff, not a free win, because it can limit gain in some circuit setups. - That tradeoff also explains why the next engineering step is reducing the non-saturating behavior. What’s next: - The team says the main next target is to reduce the non-saturating effect. - Further circuit development will determine whether CMVET devices can move from lab demonstrations to practical monolithic integrated circuits. - If the approach holds, the most likely early uses are specialized systems that need speed, radiation tolerance, and wide-temperature operation. The bottom line: - The CMVET does what earlier vacuum tubes could not: it controls current without gate leakage and already works in basic logic and amplifier circuits.