Remote Modulation Doping in van der Waals Heterostructure Transistors

Doping in two-dimensional (2D) semiconductors while suppressing Coulomb scattering is essential to achieve high-performance electronic devices. Despite recent advances in the fabrication of artificial van der Waals heterostructures and their electronic device applications, modulation doping in 2D semiconductors has not been demonstrated so far. Typically, these atomically thin materials can be easily doped by simple molecular charge transfer methods. However, the ionized dopants generated on the surface are present in close proximity to the atomically thin channel and thereby can significantly hamper the charge transport by Coulomb interaction, leading to the charged impurity scattering. Here, we demonstrate a modulation doping in the WSe₂/<i>h</i>-BN/MoS₂ heterostructure that can diminish the doping-induced scattering, in which electrons in the underlying MoS₂ channel doped by remote charge transfer are spatially separated from molecular dopants on the WSe₂ surface. Remarkably, as decreasing the temperature, <i>μ</i> of the modulation-doped (MD) device monotonically increases and begins to saturate below 100 K, whereas, for the direct-doped (DD) device, <i>μ</i> peaks around 200 K and gradually decreases as further decreasing the temperature. Such a decreasing behavior of <i>μ</i> at low temperature is not observed in the case of the undoped samples. In particular, the MD device exhibits over an order of magnitude enhancement in <i>μ</i> at 10 K from 63 to 1,100 cm²V^-1s^-1 compared with the DD counterpart. These results could be explained by the reduction of the dopant-induced charge impurity scattering.