LAUSR

DOI: 10.1002/aelm.201800720 quest in the next decade.[1–4] However, Moore’s law has approached its physical limit because silicon FETs scaling down to 10 nm gate length especially for the sub 5 nm node is difficult to have satisfactory performance caused by the severe short channel effect.[1,5,6] To extend Moore’s law down to sub 10 nm, 2D semiconductors are proposed as the next-generation channel candidates to replace silicon.[2,7–10] Their atomic thickness benefits the improvement of gate electrostatic controlling ability, and their uniform and free-dangling-bond structures lead to improved transporting efficiency.[5,11–14] The most extensively concerned 2D semiconductors are transition metal dichalcogenides (TMDs) like 2D MoS2 and black phosphorene (BP).[10,15–20] The 1 nm Lg bilayer (BL) MoS2 FET and 8.2 nm Lg monolayer (ML)/ 9.6 nm Lg multilayer MoS2 FETs are successfully fabricated.[1,3,21] However, 2D MoS2 FETs with low carrier mobility (≈270 cm2 V−1 s−1),[22–26] suffer from low on-state current (≈20 μA μm−1)[1] and thus poor device switching speed. BP FETs possess a high carrier mobility (≈1000 cm2 V−1 s−1) but are instable under ambient condition.[27–29] It is urgent to explore 2D semiconductors with high carrier mobility, air stability, and superior device performances in logic devices simultaneously. Very recently, ML, BL, and few layers Bi2O2Se are successfully fabricated on mica substrate by means of chemical vapor deposition (CVD) method.[30–32] Bi2O2Se, as a typical bismuth-based oxychalcogenide semiconductor, is composed by Bi2O2 layers and Se layers under weak electrostatic interaction.[8,22,32–34] Remarkably, 2D Bi2O2Se has an ultrahigh electron mobility (>20 000 cm2 V−1 s−1 at low temperature, ≈450 cm2 V−1 s−1 at room temperature), which exceeds that of MoS2. 2D Bi2O2Se down to monolayer shows robust stability in air, and in moist or thermal conditions.[32] Since the stability is a precondition for large-scale production, 2D Bi2O2Se is a more feasible candidate of the next-generation channel material compared with BP. So far, the ML Bi2O2Se high performance devices have not been fabricated yet due to a big contact resistance while the long channel top-gated high performance BL and few layer Bi2O2Se FETs with Au/Pd electrode have been fabricated and exhibited a large current on/off ratio (>106).[32] However, the performance upper limit of BL Bi2O2Se FET in ultrashort channel remains unknown. Therefore, it is highly desirable to explore whether sub 10 nm BL Bi2O2Se FET can meet the Due to high carrier mobility and excellent air stability, emerging 2D semiconducting Bi2O2Se is attracting much attention as a potential channel candidate for the next-generation field effect transistor (FETs). Although the fabricated bilayer (BL) and few layers Bi2O2Se FETs exhibit a large current on/off ratio (>106) and a near-ideal subthreshold swing value (≈65 mV dec−1), the performance limit of ultrashort channel Bi2O2Se FET is obscure. Here the ballistic performance upper limit of the sub 10 nm BL Bi2O2Se metal-oxidesemiconductor FETs (MOSFETs) is simulated for the first time by using ab initio quantum transport simulations. The optimized BL Bi2O2Se n-type MOSFETs can fulfill the high performance device requirements on the on-state current, delay time, and power dissipation of the International Technology Roadmap for Semiconductors in 2028 until the gate length is scaled down to 5 nm. Therefore, Moore’s law can be extended to 5 nm by taking BL Bi2O2Se as the channel.