High external emission efficiency in intentionally ordered GaInP/GaAs structures

The authors report on an additional effect of the intentionally ordered GaInP layers obtained by using the double tilt GaAs substrates, i.e., the misoriented (001) GaAs substrates toward the two directions of [110] and [−110]. In photoluminescence (PL) spectra at 7 K, it is found that the emission intensity is enhanced with the increase in the substrate misorientation angle toward [−110] direction, along with the redshift of the bandedge. However, the redshift of the bandedge means that the GaInP layers suffer from the ordering of group III atoms. The authors note that the surface morphology in the ordered GaInP layers becomes rapidly rough by the substrate misorientation, even though the linewidths of their PL spectra and x-ray rocking curves are almost similar, irrespective of the misorientation angle. As a result, the light extraction mechanism in the roughened surface structure and the surface roughening mechanism in the intentionally ordered GaInP layers are suggested.