A source of charge carriers in thin film transistor-based memory devices is provided for a memory. The source of charge carriers can include a diode having a first and second terminal. A NAND string coupled on a first end via a first switch to a bit line, is coupled on a second end via a second switch to the first terminal of the diode. Separately drivable first and second supply lines are coupled to the first and second terminals, respectively of the diode. Circuitry is included that is coupled to the first and second supply lines, that is configured to bias the first and second supply lines with different bias conditions depending on the mode of operation, including forward bias conditions and reverse bias conditions.