High-efficiency top-emitting microcavity light-emitting diodes

摘要

Abstract: Microcavity light emitting diodes (MCLEDs) present several interesting features compared to conventional LEDs such as narrow linewidth, improved directionality and high efficiency. We report here on MCLEDs with a top emitting geometry. The MCLED layers were grown using molecular beam epitaxy on GaAs substrates. They consist of a 3-period Be- doped distributed Bragg reflector (DBR) centered at 950 nm wavelength, a cavity containing three InGaAs quantum wells and a 15-periods Si-doped DBR. Different values for the wavelength detuning between spontaneous emission line and Fabry-Perot cavity mode were explored, between $MIN@40 nm and $PLU@10 nm. Devices sizes ranged from 420 $MUL 420 $mu@m$+2$/ to 22 $MUL 22 $mu@m$+2$/. As expected from simulations, the higher efficiencies are obtained when the detuning is in the $MIN@20 to 0 nm range. The devices exhibit then up to 10% external quantum efficiency, measured for a 62$DGR collection half-angle. After correction for the surface shadowing due to the grid p-contact, the efficiency increases to 14% and is practically independent of device size.!7