No abstract

First-principles calculations are performed for the recently synthesized monolayer MoSi2N4 [Science 369, 670–674 (2020)]. We show that N vacancies are energetically favorable over Si vacancies, except for Fermi energies close to the conduction band edge in the N-rich environment, and induce half-metallicity. N and Si vacancies generate magnetic moments of 1.0 and 2.0 μB, respectively, with potential applications in spintronics. We also demonstrate that N and Si vacancies can be used to effectively engineer the work function.

No abstract

Two-dimensional semiconductors have great potential in high-performance electronic devices. However, the common way of contacting them with metals to inject charge carriers results in contact resistance. We propose a junction-free field-effect transistor consisting of semiconducting monolayer blue phosphorene as channel material (with high carrier mobility) and metallic bilayer blue phosphorene as electrodes. The junction-free design minimizes the contact resistance. Employing first-principles calculations along with the non-equilibrium Green’s function method, we demonstrate a high Ion/Ioff ratio of up to 2.6 × 104 and a remarkable transconductance of up to 811 μS/μm.

Gate controllability is a key factor that determines the performance of GaN high electron mobility transistors (HEMTs). However, at the traditional metal‐GaN interface, direct chemical interaction between metal and GaN can result in fixed charges and traps, which can significantly deteriorate the gate controllability. In this study, Ti3C2Tx MXene films are integrated into GaN HEMTs as the gate contact, wherein van der Waals heterojunctions are formed between MXene films and GaN without direct chemical bonding. The GaN HEMTs with enhanced gate controllability exhibit an extremely low off‐state current (IOFF) of 10−7 mA mm−1, a record high ION/IOFF current ratio of ≈1013 (which is six orders of magnitude higher than conventional Ni/Au contact), a high off‐state drain breakdown voltage of 1085 V, and a near‐ideal subthreshold swing of 61 mV dec−1. This work shows the great potential of MXene films as gate electrodes in wide‐bandgap semiconductor devices.