Flexible GaAs Photodetectors with Ultrathin Thermally Grown Silicon Dioxide as a Long­Lived Barrier for Chronic Biomedical Implants

Abstract

Herein, an approach to form high-quality GaAs-based flexible photodetectors (PDs) is first demonstrated by metal wafer bonding (MWB) and high-throughput epitaxial lift-off (ELO) with encapsulated thermally grown silicon dioxide (t-SiO2) for chronic biomedical implants. The flexible GaAs PDs demonstrate responsivity over a wide range of visible and near-infrared wavelengths. Regarding certain diagnoses, high-performance PDs are essential for precise treatments with longterm optoelectronic implants, and the long-term stability and reliable encapsulation of GaAs PDs will play a major role when optoelectronics are injected into biofluids. t-SiO2, as an encapsulation barrier, is stable without increasing the leakage current for over 120 h in phosphate-buffered saline (PBS) at 70 C. By Arrhenius scaling, the device shows a 700-day lifetime with stable operation in a biofluid at 37 C. Finally, by measuring the mass of arsenic using an inductively coupled plasma mass spectrometer (ICP/MS), the t-SiO2 encapsulation barrier is capable of preventing toxic elements from leaching out to surrounding tissues. The technology may provide approaches based on III？V materials for expanding high-performance optoelectronic devices to biomedical implants, namely, a broad range of high-resolution retinal prostheses for blindness or the integration for measuring physiological parameters, such as tissue oxygenation and neural activity in the cerebral cortex.