One or more of the following elements may be included to increase the probability that shorter wavelength photons generated by EL may be absorbed in the longer wavelength QWs.

A dichroic mirror may be coated on one or more external surfaces of the LED chip. The dichroic mirror may have a high reflectivity at the shorter wavelength of EL emissions and a low reflectivity at the longer wavelength of PL emissions over a wide range of angles of incidence.

A photonic crystal may be patterned into one or more external or internal surfaces of the LED. The periodicity of the photonic crystal may be selected to minimize diffraction of the shorter wavelength EL emissions and maximize diffraction of the longer wavelength PL emissions.

An epitaxial mirror may be grown within the epitaxial layer structure of the LED wafer. This epitaxial mirror may have a higher angle-averaged reflectivity for the shorter wavelength EL emissions as compared to the longer-wavelength PL emissions.

A distributed Bragg reflector (DBR) may be integrated into the wafer. The DBR may be formed by the growth of a sequence of epitaxial layers with differences in doping and/or alloy composition combined with a post-growth electrochemical reaction. The post-growth reaction may be selective with respect to doping and/or alloy composition and may reduce the effective refractive index of some of the layers in the epitaxial sequence. The thickness of the epitaxial layers may be chosen to result in a DBR periodicity that maximizes reflectivity corresponding to the shorter wavelength of EL emissions.

The distance between the reflecting electrode described above and the EL emitting QWs may be selected to control the internal radiation angular distribution of the EL emissions in a way that maximizes its absorption in the PL emitting QWs.