Temperature and thickness dependences of electron nonradiative transitions in GaInNAs/GaAs SQW investigated by piezoelectric photothermal spectroscopy

Recently, GaInNAs/GaAs single quantum well (SQW) structures have been considered as a new candidate material for an effective infrared LED for optical fibre communications. In order to investigate the electron nonradiative transitions in the GaInNAs SQW layer, piezoelectric photothermal (PPT) spectroscopy was used. The thickness- and the temperature-dependences of the PPT signal for the samples of thickness 10, 5 and 3 nm and from 300 K down to 77 K were investigated. The PPT spectra show a blue shift of the exciton and band-to-band transition with decreasing sample thickness. This was explained by quantum mechanical discussions for the confinement of the charge carriers supposing an electron effective mass of 0.08 m₀ and band offset ratio of 6:4. The effect of the induced strain in the quantum well on the electronic structure is also discussed. The decreasing temperature also exhibits a blue shift of the PPT signal peaks and a decrease of the PPT signal amplitude. The temperature variation shows that the nonradiative intraband transition between the heavy and the light hole bands causes the additional contribution to the signal. It is concluded that the present PPT technique is an effective methodology for measuring the electron transitions in the SQW.