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

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‐SiO 2 ) 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 long‐term 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‐SiO 2 , 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‐SiO 2 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.