Highly accurate tuning of current–voltage characteristic shift in a photo-sensitive three terminal metal–insulator–semiconductor device

We present a planar three terminal device fabricated on a silicon-on-insulator substrate. The device is based on a two-layer dielectric stack comprising SiO2 tunneling and HfO2 layers. A so-called gate electrode is placed between two other contacts, of the source and drain, all deposited on the insulator stack. In the dark as well as under illumination, the current–voltage characteristic can be shifted in an ideal linear manner with changes in a positive gate voltage with the shift being somewhat larger under illumination. The reason for the change of shift is the ability of high-density oxygen vacancies, arranged in the filament regions within an HfO2 sublayer that was voltage stress. Namely, holes or electrons are trapped in the HfO2 sublayer, respectively, from the inverted or accumulated Si layer. This process is controlled by the gate and drain bias levels. Moreover, under illumination and at negative gate and drain voltages, the device exhibits negative differential resistance caused by capture of photo-generated minority carriers induced in the depletion region of the Si after they tunnel through the SiO2 layer by negative oxygen vacancies that migrate to the SiO2/HfO2 interface through the filament regions. Finally, the low level of saturation current in the dark and the ability to precisely control its value by illumination intensity, together with a large sensitivity of 80–85 A/W and 25 A/W, at 490 nm and 365 nm, respectively, allow additional applications that cannot be achieved with conventional MIS devices.