Guided-Mode Resonator Coupled with Nanocrystal Intraband Absorption

Intraband absorption in doped nanocrystals offers an interesting alternative to narrow-band-gap materials to explore mid-infrared optoelectronic device designs. However, the performance of such a device clearly lags behind the ones relying on intrinsic materials. Livache et al. proposed a dye-sensitized approach to overcome the limitations observed from intraband materials (high dark current, slow response, low activation energy), where an intraband absorber is coupled with an undoped material, which takes care of the charge conduction. Here, we unveil the coupling between both materials using mid-infrared transient reflectivity (TR) measurement. We show that the hybrid material displays a unique feature in the TR signal that we attribute to a charge transfer for which the dynamics matches the hopping time. Then, we developed a strategy to enhance the photodetection performances of the hybrid material by coupling the intraband absorption to a light resonator for the first time. The latter is used to enhance the absorption by a factor of 4 and enables an increase in the operating temperature by 80 K compared to the reference device. The obtained device matches the performance of the best devices relying on intraband absorption.