Study on high radiance surface emitting LED with corner reflector and its integration with microlenses

Abstract

We have studied on the high radiance surface emitting LED. To overcome the problems in conventional SE-LED such as low external quantum efficiency, low optical coupling efficiency to optical fiber and easy saturation phenomenon by in-plane radiation, new LED structure with 45° circular corner reflector, deeply etched side-wall and microlenses is developed. New fabrication technologies of microlenses using UV curing method and chemical etching process are developed. Using AFM, Whit Light Interferometer, SEM, Focused Spot Size measurements and etc, we checked the performances and qualities of microlenses. To show the applications of the microlenses, we made a microlensed SE-LED and a hemispheric lensed fiber, and various micro-optics and its arrays. In Chapter 3, SE-LED with 45° circular corner reflector(CR-LED) was simulated and fabricated. From the simulation, we could estimate that the output power of new structure LED increase about 4 times rather than the conventional surface emitting LED due to extraction of in-plane radiation. Shadow masked growth with monocrystalline mask(InP/InGaAs) and chemical etching of InP/InGaAsP/InGaAs using 1 HBr:$1H_3PO_4$:$0.5(0.5M)K_2Cr_2O_7$ are studied for fabrication of 45° corner reflector. In light-current curve measurement, the output power of CR-LED increased several times than that of conventional SE-LED. In the spectra characteristics, we could observe the peak that comes from extraction of in-plane radiation by corner reflector. In the near field pattern, the bright ring that come from in-plane radiation by corner reflector was observed. In chapter 4, we had newly proposed and fabricated high radiance Bell Shaped LED(BS-LED) with 45° corner reflector, deeply etched side wall and microlens. We simulated the improvement of output power by side wall as three variable parameters, the radius of p-metal(R1), the width of space region(R2) and the depth of side wall. The deeply etched side-wall was formed by $1HBr-1H_3PO_{...