Improvement of efficiency droop of GaN-based light-emitting devices by a rear nitride reflector

GaN-based light-emitting devices (LEDs) with and without a rear distributed Bragg reflector (DBR) were grown by metal-organic chemical vapor deposition. The integrated electroluminescence (EL) intensity of LED with a rear nitride DBR showed a super-linear increase up to a current density of 135 A/cm(2) and the relative external quantum efficiency (EQE) kept monotonously increasing with increase in injection current density. For the LED without a rear DBR, however, the emission efficiency reached the maximum at a very low current density of 10 A/cm(2). The improvement is mainly attributed to reflection of light from the DBR to the "top side" and decrease in light absorption in the active region with increase in injection current density. Moreover, the improvement in relative EQE was attributed to the resonant cavity enhancing spontaneous emission at its resonant wavelength too. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.