An embodiment includes an apparatus comprising: a substrate; a thin film transistor (TFT) comprising: source, drain, and gate contacts; a semiconductor material, comprising a channel, between the substrate and the gate contact; a gate dielectric layer between the gate contact and the channel; and an additional layer between the channel and the substrate; wherein (a)(i) the channel includes carriers selected from the group consisting of hole carriers or electron carriers, (a)(ii) the additional layer includes an insulator material that includes charged particles having a polarity equal to a polarity of the carriers. Other embodiments are described herein.