Photoluminescence excitation spectroscopy of MBE grown InGaN quantum wellsand quantum boxes

Photoluminescence excitation (PLE) spectroscopy was carried out to investig ate the excitation/emission cycle of MBE grown InGaN quantum structures. Qu antum well and Stranski-Krastanov type quantum box samples were chosen that emit from blue to red. The bandgap energy (E-g), determined from the PLE s pectrum, was found to decrease concurrently with the detection energy. This indicates that the emission spectrum from the sample is inhomogeneously br oadened. A plot of the resultant Stokes shift against detection energy show s a linear trend. Our results agree with those from independent measurement s of thermally detected optical absorption (TDOA) in some of the samples. O n comparison with absorption and PLE measurements on MOCVD grown InGaN. a d ifference in the bandgap energies obtained becomes apparent for detection e nergies below approximate to 2.6 eV.