Active Region Based on GradedGap InGaN/GaN Superlattices for HighPower 440 to 470nm LightEmitting Diodes

In this study, we grew and investigated LED struc� tures with an active region of new design based on sev� eral ultrathin InGaN layers in a GaN matrix limited from both sides by InGaN/GaN shortperiod super� lattices (SPSLs) of either constant or variable (graded� gap SPSLs) composition with respect to indium. The structural properties of the SPSLs and active region were studied by highresolution transmission electron microscopy (TEM), secondaryion mass spectrome� try (SIMS), and Xray diffraction (XRD). The optical properties of the structures were analyzed by the pho� toluminescence (PL) and electroluminescence (EL) methods. Abstract—The structural and optical properties of lightemi tting diode structures with an active region based on ultrathin InGaN quantum wells limited by shortpe riod InGaN/GaN superlattices from both sides have been investigated. The dependences of the external quantum efficiency on the active region design are ana� lyzed. It is shown that the use of InGaN/GaN structures as limiting gradedgap shortperiod superlattices may significantly increase the quantum efficiency.