Integrated tunable surface acoustic wave with quantum well structure technology and systems provided thereby

摘要

A ZnO monolithically integrated tunable surface acoustic wave (MITSAW) device uses tunable acousto-electric and acouso-optic interaction between surface acoustic waves (SAW) and a two dimensional electron gas (2DEG) in a ZnO/Mg_xZn_1−xO quantum well. The high electromechanical coupling coefficients of piezoelectric ZnO in conjunction with the low acoustic loss and high velocity of sapphire (Al₂O₃) offers high frequency and low loss RF applications. The 2DEG interacts with the lateral electric field resulting in ohmic loss which attenuates and slows the surface acoustic wave. This mechanism is used to tune the acoustic velocity. The high coupling coefficients offered by the ZnO/R—(Al₂O₃) systems allows large velocity tuning. Combined with the optical characteristics of the wide and direct band gap (about 3.3 eV) semiconductor and transparent ZnO electrodes, the MITSAW chip can be used for UV optical signal processing. R-plane sapphire is chosen instead of the popular C-plane substrate, as this substrate provides in-plane anisotropy in the ZnO layer. ZnO MITSAW technology not only improves existing devices but also develops many important application areas, such as tunable/adaptive filters, voltage-controlled oscillators, zero-power remote wireless sensors, and fixed and tunable UV optical delay lines.