**Abstract**

Biological detection based on surface plasmon resonances (SPRs) on metallic Ga-doped zinc oxide (ZnO: Ga) film surfaces is introduced as one of the interesting functionalities of ZnO. SPRs on ZnO: Ga films (ZnO-SPRs) have attracted much attention as alternative plasmonic materials in the infrared (IR) range. This chapter focuses on the structure and optical properties of ZnO-SPR with different layer structure from experimental and theoretical approaches. First, the plasmonic properties of single ZnO: Ga films excited by Kretschmann-type SPRs were investigated. Second, an insulator–metal–insulator structure with a ZnO: Ga film applied as a metal layer is introduced. Finally, hybrid layer structures with the capping of thin dielectric layers to ZnO-SPR (dielectric-assisted ZnO-SPR) were fabricated to enhance SPR properties in the IR range. The biological sensing on ZnO-SPR is experimentally demonstrated by measuring biological interactions. This work provides new insights for fabricating biological sensing platforms on ZnO materials.

**Keywords:** oxide semiconductor, surface plasmon, near-infrared, biological detection, zinc oxide, heterointerface
