EQE Measurements in Mid-Infrared Superlattice Structures

LEDs which emit in the mid-infrared have low efficiency. This limits their applications in military infrared systems as well as potential uses in gas sensing. These problems are the impetus for EIRE, which stands for Efficient InfraRed Emitters. EIRE seeks to solve the efficiency problems through the use of III-V superlattices as an emission material. My part in this project was to measure the External Quantum Efficiency (EQE) of the superlattice structures we grew, which is key in developing more efficient devices. This was done using photoluminescence, where the superlattice is excited by a laser beam and the emitted light measured. The EQE values measured for these structures corresponded to an Internal Quantum Efficiency (IQE) of nearly 40%, which is impressive for mid-IR emitters. Making these measurements involved learning to use vacuum and cryogenic equipment as well as troubleshoot optical setups. I also helped write python programs to control the experimental setup and analyze the data. The data I helped collect will go towards growing more efficient superlattice structures in the future.