Two-dimensional semiconductors, such as transition metal dichalcogenides, have demonstrated tremendous promise for the development of highly tunable quantum devices. Realizing this potential requires low-resistance electrical contacts that perform well at low temperatures and low densities where quantum properties are relevant. Here we present a new device architecture for two-dimensional semiconductors that utilizes a charge-transfer layer to achieve large hole doping in the contact region, and implement this technique to measure the magnetotransport properties of high-purity monolayer WSe₂. We measure a record-high hole mobility of 80,000 cm² V^–1 s^–1 and access channel carrier densities as low as 1.6 × 10¹¹ cm⁻², an order of magnitude lower than previously achievable. Our ability to realize transparent contact to high-mobility devices at low density enables transport measurements of correlation-driven quantum phases including the observation of a low-temperature metal–insulator transition in a density and temperature regime where Wigner crystal formation is expected and the observation of the fractional quantum Hall effect under large magnetic fields. The charge-transfer contact scheme enables the discovery and manipulation of new quantum phenomena in two-dimensional semiconductors and their heterostructures.

二维半导体，例如过渡金属二硫属化物，已经显示出开发高度可调量子器件的巨大前景。实现这一潜力需要低电阻电接触，在与量子特性相关的低温和低密度下表现良好。在这里，我们提出了一种用于二维半导体的新器件架构，它利用电荷转移层在接触区域实现大空穴掺杂，并利用该技术来测量高纯度单层WSe ₂的磁输运特性。我们测得空穴迁移率创历史新高，达到 80,000 cm ² V ^–1 s ^–1 ，接入沟道载流子密度低至 1.6 × 10 ¹¹ cm ^-2 ，比以前可达到的数量级低一个数量级。我们能够在低密度下实现与高迁移率器件的透明接触，从而能够对相关驱动的量子相进行传输测量，包括在预期形成维格纳晶体的密度和温度范围内观察低温金属-绝缘体转变以及观察大磁场下分数量子霍尔效应的研究。电荷转移接触方案使得能够发现和操纵二维半导体及其异质结构中的新量子现象。