Generation and enhancement of surface acoustic waves on a highly doped p-type GaAs substrate

Surface acoustic waves (SAWs) have been widely studied due to their unique advantage to couple the mechanical, electrical, and optical characteristics of semiconductor materials and have successfully been used in many industrial applications. In this work, we report a design that uses piezoelectric material Zinc Oxide (ZnO) to enhance the generation and propagation of SAWs on the surface of a highly doped p-type Gallium Arsenide (GaAs) substrate, which is more extensively used in optoelectronic devices than intrinsic GaAs structures. To maximize the piezoelectricity and successfully generate SAWs, high quality c-axis orientation of the ZnO film is needed; thus we experiment and develop optimized recipes of a radio frequency (RF) magnetron sputtering system to deposit ZnO on the GaAs substrate. To further optimize the SAW performance, an intermediate Silicon Oxide (SiO₂) layer is added between the ZnO film and GaAs substrate. Additionally, we test samples with varied thickness of ZnO films and dimensions of interdigital transducer (IDT) fingers to figure out their individual effect on SAW properties. The results and techniques demonstrated in this paper will provide guidance for further studies on enhancing SAWs propagating along many other doped semiconductor materials. This combination of acoustics and optoelectronics in doped semiconductors is a promising start to building enhanced and hybrid devices in various fields.