Optical properties of semiconductor quamtum structures for optoelectronic devices

Optical properties of semiconductor quamtum structures for optoelectronic devices Department of Applied Physics and Chemistry Associate Professor Tsuyoshi OKUNO okuno@pc.uec.ac.jp
We are studying the optical properties of semiconductor quantum structures for future optoelectronic devices. Zero-dimensional quantum dots and other structures are investigated.
		Understanding of carrier dynamics in quantum structures is essential for the application to ultrafast electronic or bright and fast optical devices. Figure 1 shows photoluminescence excitation spectra of CdTe quantum dots. The 19th order optical phonon structure is observed, and is the highest one among the reported material systems so far including bulk, quantum wells, and dots. This indicates fast exciton relaxation from matrix to dots, as well as strong carrier confinement and strong electron-phonon coupling in quantum dots.
Direct observation of temporal photoresponse is performed in low-temperature grown GaAs film. Results of the pump-probe measurements using double-pulses are shown in Figure 2. Because of the suppression of the slow tail component, no pattern effect is recognized for the separations of 7.6 and 10 ps. The feasibility of high repetition switching more than 100 GHz is demonstrated.
For all-optical switches necessary for high bit rate optical communication, optical nonlinear properties of semiconductor quantum structures having large nonlinearity and fast photoresponse are explored. In order to realize efficient light sources or new optical phenomena, research on interaction between optical centers and nanometer-scale matrices is initiated.