Photoluminescence efficiency of zincblende InGaN/GaN quantum wells

Growing green and amber emitting InGaN/GaN quantum wells in the zincblende, rather than the wurtzite,
crystal phase has the potential to improve efficiency. However, optimisation of the emission efficiency of these
heterostructures is still required to compete with more conventional alternatives. Photoluminescence time
decays were used to assess how the quantum well width and number of quantum wells affect the recombination
rates, and temperature dependent photoluminescence was used to determine the factors affecting recombination
efficiency. The radiative recombination lifetime was found to be approximately 600 ps and to increase
weakly with well width, consistent with a change in the exciton binding energy. The relative efficiency at
room temperature was found to increase by a factor of five when the number of wells was increased from
one to five. Furthermore, the efficiency increased by factor 2.2 when the width was increased from 2:5nm
to 7:5nm. These results indicate that thermionic emission is the most important process reducing efficiency
at temperatures in excess of 100 K. Moreover, the weak dependence of the rate of radiative recombination
on well width means that increasing well thickness is an effective way of suppressing thermionic emission
and thereby increasing efficiency in zincblende InGaN/GaN quantum wells, in contrast to those grown in the
wurtzite phase.