Si membrane-ZnO heterojunction-based broad band visible light emitting diode for flexible optoelectronic devices

Flexible photonics on Si complementary metal-oxide-semiconductor platforms are promising to replace conventional, brittle and rigid components for advanced applications that require mechanically agile devices. In this report, we demonstrate a mechanically flexible n-ZnO/p-Si membrane heterojunction electroluminescent device, emitting broad band visible photons at room temperature under a low operating voltage. Highly flexible and ultra-thin p-Si membranes of similar to 5.0 mu m thickness have been fabricated using a simple and cost effective alkaline etching method, followed by n-ZnO deposition by RF sputtering to form the heterojunction. The fabricated flexible heterojunction exhibits excellent rectification behavior and electroluminescence in a wavelength range of 400-850 nm at room temperature under forward bias condition. The origin of the broad emission is discussed in detail with the analysis of photoluminescence spectra and energy band alignment under an applied bias. This demonstration of broad band, visible light emission in mechanically flexible n-ZnO/p-Si heterojunction could open up innovative opportunities to integrate Si-based mechanically flexible optical sources for practical applications.