Light extraction improvement in GaAs light-emitting diodes for teraherz upconversion imaging

Thanks to the terminal optical readout mode rather than the electrical readout mode that relies on traditional readout circuits, upconversion pixelless imaging devices have great potential for photon-type imaging in the infrared/terahertz field. However, the lack of upconversion efficiency has seriously hindered the practical application of high-resolution imaging in specific high-speed usage scenarios. The extremely low external quantum efficiency of LEDs in upconversion devices severely limits the overall up-conversion efficiency of the devices. This paper presents a feasible approach to improve the quantum efficiency of LEDs by using surface microstructure. The luminescence characteristics of three kinds of LEDs with different surface microstructures at low temperature, including electroluminescence efficiency, luminescence spectrum and surface electroluminescence uniformity, were systematically studied. Experiments show that the electroluminescence efficiency (ELE) of our designed structure is up to 55% higher than that of the planar structure at low temperature and low current, and has good monochromaticity and luminous uniformity. The enhancement effect of different structures may be caused by the interaction between dipoles and collective effects. This work provides theoretical explanation and experimental basis for improving the external quantum efficiency of LED by designing surface microstructure, and provides an important idea for optimizing upconversion pixelless photon imaging technology.