Complementary Circuits with WSe₂/Organic Semiconductor Heterostructure Field-Effect Transistors

A device architecture based on heterostructure WSe₂/organic semiconductor field-effect transistors (FETs) is demonstrated in which ambipolar conduction is virtually eliminated, resulting in essentially unipolar FETs realized from an ambipolar semiconductor. For p-channel FETs, an electron-accepting organic semiconductor such as hexadecafluorocopperphthalocyanine (F₁₆CuPc) is used to form a heterolayer on top of WSe₂ to effectively trap any undesirable electron currents. For n-channel FETs, a hole-accepting organic semiconductor such as pentacene is used to reduce the hole currents without affecting the electron currents. Off-currents are reduced in FETs with heterolayers compared to WSe₂ FETs without organic heterolayers, which will decrease static power dissipation in complementary circuits. In all FETs reported in this work, the organic heterolayers cover only part of the channel, which results in more effective trapping of the carrier type that must be reduced. This device design approach can be effectively combined with p-type doping and contact metal engineering to improve WSe₂ based FETs and circuits. Complementary inverters realized with such heterostructured FETs exhibit excellent transfer characteristics. This design approach is also applicable to other ambipolar semiconductors besides WSe₂.