Abstract

It is now clear that the internal spontaneous emission quantum efficiency (η) needs to be close to unity in order to reduce the photon-number noise in semiconductor lasers below the classical limit and in order to demonstrate single- mode (thresholdless) LED operation. We use a novel method for measuring 1−η and conclude that in a high quality GaAs/AlGa As double heterostructure η can be as high as 99.7%. Our GaAs/AIGaAs double heterostructure is separated from the absorbing parent substrate by using the epitaxial liftoff technique and is then mounted on a reflecting substrate. The idea is that spontaneously emitted photons are sent into free space where they can be measured, internally absorbed and reemitted, or absorbed and dissipated to heat in the surroundings. We show that in our configuration the external quantum efficiency, η_ext (deduced from integrated photoluminescence measurements), is a sensitive measure of the non-radiative recombination rate 1−η provided that other, parasitic, absorption losses are small. Our highest measured value η_ext = 72%, which to our knowledge is by far the highest for spontaneous emission ever measured for GaAs, is explained by an average number of 25 photon regeneration processes with η = 99.7% efficiency.

© 1992 Optical Society of America