Optical properties of cation-substituted zinc oxide.

Zinc oxide (ZnO)-based optoelectronics has emerged as a frontier area in semiconductor research in recent years. In the design of ZnO-based optoelectronic devices, cation-substituted ZnO serves as essential components for the desired device functions. Band-gap engineering by cation substitution enables the facile preparation of barrier layers and quantum wells in device structures. Wurtzite solid solutions Zn 1- x Mg x O, Zn 1- x Cd x O, and Zn 1- x Be x O have been reported as examples where band gaps are gradually modulated as functions of x. In this contribution, we present an overview of composition-dependent band-gap variations of Zn 1- x M x O solid solutions. In addition, we describe the optical properties and microstructural evolution in polycrystalline Zn 1- x Mg x O (0 <or= x <or= 0.15). It is proposed that chemical strain associated with cation substitution has an impact on the band-gap magnitude, crystallite morphology, and optical defects.