Extended Data Fig. 1: Device structure and band diagrams in different operational modes.

Schematic illustration of the device structure from the sectional view. The injection transistor (shorter channel and higher threshold voltage) and the read transistor (longer channel and lower threshold voltage) are parallelly connected: they have a common drain and a common floating gate; their sources are externally shortened. The capacitance between the floating gate and the drain (\(C_{GD}\) is much larger than other capacitances), thus the floating gate voltage is mainly coupled to the drain. (b) The equivalent circuit symbol of the device. (c) Band diagrams of the read transistor in the reading mode. A low drain voltage will induce a low floating gate voltage and keep the transistor closed. As the drain voltage increases, the floating gate voltage increases, and the transistor gradually opens. The injection transistor shares similar behaviour but has a lower current since the threshold voltage is higher. (d) The band diagram of the injection transistor at the depression (program) mode. When a higher voltage is applied to the drain and the source is grounded, the electrons in the channel are accelerated by the electrical field in the drain region, and the lucky ones are injected into the floating gate, that is, channel hot electron injection (CHEI). (e) The band diagram of the injection transistor in the potentiation (erase) mode. When a higher voltage is applied to the source and the drain is grounded or floating, the source p-n junction is reversely biased. This induces band-to-band (B2B) hole generation in the source region. The high lateral electric field accelerates the generated holes, and the lucky ones are injected into the floating gate. The hot electron/hole effects are negligible in the readout transistor.