GeSn μ-LED Array with Programmable Spectra for Near-Infrared Microspectrometer

Spectrometers are important analytical instruments in research fields involving light and matter, and their miniaturization is critical for portable and on-chip applications. Spectrometers based on computational reconstruction of spectra are among the most promising technologies for footprint reduction. Of the various reconstruction methods, those that require programming of the light source are particularly challenging to realize. In this work, by exploiting the gradient-composition characteristic of a single GeSn strip grown using the rapid melting growth method, near-infrared microscale light-emitting diodes (mu-LEDs) with different peak wavelengths were fabricated. The spectra of the GeSn mu-LEDs, which are integrated on a Si substrate, can be programmed in the range of 1.6 to 2.4 mu m to realize a prototype reconstructive spectrometer by controlling the injection current of the individual LEDs. In this way, as an example, the absorption spectrum of water was successfully reconstructed simply by programming the spectra of the light source. These results provide a completely new technological roadmap for the miniaturization of spectrometers.