We demonstrate the formation of large sheets of layered organic-inorganic perovskite (OIPC) crystals, as thin as a single unit cell, prepared by mechanical exfoliation. The resulting 2D OIPC nano sheets of 2.4 nm thickness are direct semiconductors with an optical band gap of 2.4 eV. They exhibit unusually strong light-matter interaction with an optical absorption as high as 25% at the main excitonic resonance, as well as bright photoluminescence. We extract an exciton binding energy of 490 meV from measurement of the series of excited exciton states. The properties of the excitons are shown to be strongly influenced by the changes in the dielectric surroundings. The environmental sensitivity of these ultrathin OIPC sheets is further reflected in the strong suppression of a thermally driven phase transition present in the bulk crystals.

We present results on optimized growth temperatures and layer structure design of high mobility photoconductive Terahertz (THz) emitters based on molecular beam epitaxy grown In0.53Ga0.47As/In0.52Al0.48As multilayer heterostructures (MLHS). The photoconductive antennas made of these MLHS are evaluated as THz emitters in a THz time domain spectrometer and with a Golay cell. We measured a THz bandwidth in excess of 4 THz and average THz powers of up to 64 μW corresponding to an optical power-to-THz power conversion efficiency of up to 2 × 10−3.

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We investigate properties of MBE grown photoconductive terahertz (THz) antennas based on the InGaAs/InAlAs/InP material system aimed for an excitation wavelength of approx. 1060 nm. Therefore, we analyze several different approaches concerning growth parameters, layer and material compositions as well as doping. The carrier dynamics are probed via transient white-light pump-probe spectroscopy as well as THz Time Domain Spectroscopy (TDS) measurements. We find that the electron capture probability is reduced for higher electron energies. By adjusting the material band gap this can be resolved and lifetimes of 1.3 ps are obtained. These short lifetimes enable the detection of THz TDS spectra with a bandwidth exceeding 4 THz