16.8 % external quantum efficiency from a planar LED

Efficient, cheap, and simple, LEDs are used in many applications and make up the bulk of the opto-electronic component market. Due to the small critical angle at the semiconductor-air interface, relatively little light escapes per facet. The conventional route is to collect light from all six facets and redirect it, using external reflectors into a useful direction. While this increases external quantum efficiency it does little to increase brightness. In the last few years the microcavity approach has been used to persuade the light to leave by just one facet, thus increasing the brightness considerably. Although remarkable efficiencies have been achieved, microcavity LEDs (MCLEDs) have yet to surpass conventional LEDs. We present here a single mirror LED (SMLED), grown by MBE, which falls between the conventional LED and the planar MCLED. The top mirror is a non-alloyed Au layer deposited on a highly doped GaAs phase-match-layer. This is followed by a single Bragg pair of GaAs/Al(0.6)Ga(0.4)As p-doped. The active region is comprised of one InGaAs 7 nm wide QW embedded in a lambda thickness of Al(0.1)Ga(0.9)As. On the substrate side carrier confinement is given by a lambda/2 AlAs layer n-doped on an n(+)-GaAs substrate. The emission reflected by the p-side mirror interferes constructively with the emission through the substrate, giving a 4-fold increase in power per facet The actual device performance is 16.8 % external quantum efficiency and this exceeds expectations and can be accounted for by significant photon recycling.