Wafer-scale growth of two-dimensional, phase-pure InSe

Two-dimensional (2D) indium monoselenide (InSe) has attracted sig-nificant attention as an ultrathin III-VI semiconductor with a combi-nation of favorable attributes that are comparable to those of III-V semiconductors and van der Waals 2D transition-metal dichalcoge-nides. Nevertheless, there has been no demonstration of large -area synthesis of 2D InSe due to the complexity of the binary In-Se system and the difficulties in promoting lateral growth. Here, we report the polymorph-selective synthesis of epitaxial 2D InSe by metal-organic chemical vapor deposition (MOCVD) over 2-in wafers. We achieve polymorph-selective epitaxial growth of InSe on c-plane sapphire via flow modulation to control the Se/In ratio. The layer-by -layer growth allows thickness control with tunable optical proper-ties comparable to those of bulk crystals. We also demonstrate gate-tunable electrical transport with a field-effect mobility compa-rable to that of single-crystalline flakes. These results indicate that InSe grown by MOCVD could be an effective channel material for back-end-of-line integration in logic transistors.