Growth Strategy and Physical Properties of the High Mobility P-Type CuI Crystal

Acquiring stable binary wide band-gap semiconductor (WBS) materials with high p-type mobility is essential for the development of WBS optoelectronic devices. CuI is a p-type WBS material with a large band gap (3.1 eV) and high exciton binding energy (62 meV). However, the semiconductor characteristics of the CuI single crystal are unknown due to the lack of a large sized and high quality crystal. Our approach focuses on the design of the mineralizer for the hydrothermal method to effectively control the growth habit and the impurity concentration in the crystal. A large size (15 mm × 10 mm × 1 mm) and high quality CuI single crystal is obtained by using a new mineralizer (NH 4 I + KI). The crystal shows high p-type mobility (43.9 cm 2 ·V −1 ·S 1− ). The strong and sharp band-edge emission at 410 nm indicates that the interband excitonic transition dominates the optical response in the spectrum. Such a binary crystalline material may open the way to new applications in optoelectronic devices.