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

Abstract

Herein, an approach to form high­quality GaAs­based flexible photodetectors (PDs) is first demonstrated by metal wafer bonding (MWB) and high­throughput epitaxial lift­off (ELO) with encapsulated thermally grown silicon dioxide (t­SiO2) for chronic biomedical implants. The flexible GaAs PDs demonstrate responsivity over a wide range of visible and near­infrared wavelengths. Regarding certain diagnoses, high­performance PDs are essential for precise treatments with long­term optoelectronic implants, and the long­term stability and reliable encapsulation of GaAs PDs will play a major role when optoelectronics are injected into biofluids. t­SiO2, as an encapsulation barrier, is stable without increasing the leakage current for over 120？h in phosphate­buffered saline (PBS) at 70？°C. By Arrhenius scaling, the device shows a 700­day 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 t­SiO2 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 high­performance optoelectronic devices to biomedical implants, namely, a broad range of high­resolution retinal prostheses for blindness or the integration for measuring physiological parameters, such as tissue oxygenation and neural activity in the cerebral cortex.