Low temperature processed p‐type bottom gate microcrystalline silicon thin film transistors

Abstract

We report on processing of p‐type bottom gate microcrystalline silicon thin film transistors (p‐type BG TFT). In particular, we demonstrate that a thermal annealing at 250 °C is required to get ideal contacts, regardless of the drain‐source met al. We found that aluminium is the best suited metal for source and drain contacts, as in the case of n‐type thin film transistors.The TFTs mobility and sub‐threshold slope (V/dec) are improved when a hydrogen plasma treatment was applied to the a‐SiN:H prior to µc‐Si deposition. Our best p‐type BG TFTs exhibit a field effect mobility of ∼ 1.2 cm2/Vs, a sub threshold slope of ∼1V/dec and an ON/OFF ratio of 105 while keeping a stable threshold voltage (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ambipolar a-SiGe:H thin-film transistors fabricated at 200°C

“…For this application, the use of complementary devices, n-and p-type transistors, is attractive since this technology allows for the implementation of efficient digital circuits. Although complementary metal oxide semiconductor (CMOS) logic circuits, based on separated n-and p-type doped deposited layers, are currently under development [1], the use of ambipolar TFTs, operating as either p-or n-type transistors, can simplify the design and reduce the cost for the fabrication of the complementary logic circuits. Hydrogenated amorphous silicon (a-Si:H) has been typically used as the active layer of TFTs.…”

Development of Low-Temperature Ambipolar a-SiGe:H Thin-Film Transistors Technology

“…As opposed to unipolar silicon metal oxide semiconductor (MOS) devices whose p-type or n-type behavior is determined during fabrication, ambipolar devices can be switched from p-type to n-type by changing the gate bias. Although complementary thin-film CMOS logic circuits, based on separated n-and p-type doped deposited layers, are currently under development [17], the use of ambipolar TFTs can simplify the design and reduce the cost for the fabrication of the complementary logic circuits. Ambipolar and unipolar conductions are illustrated by the transfer curves of TFTs in Figure 1.2.…”