Modeling of light-sensitive resonant-tunneling-diode devices

We present a method to include the effects of light excitation on two different models of resonant-tunneling-diode-based devices. Our approach takes into account both photoconductive and charge accumulation effects responsible for shifting the static I –V curve when the structure is under light excitation. Computational simulations led to good agreement between the model and experimental result

Superhigh-frequency characteristics of optical modulators on the basis of InGaAlAs resonance-tunnel heterostructures

The impedance of InGaAlAs resonance-tunnel heterostructures used for modulation of optical radiation is experimentally studied in the frequency range from 45 to 18 MHz. The dependence of their equivalent circuit on the bias voltage is determined. The spectrum of the harmonics of the current in the resistive frequency multiplication in such structures is calculated. The results confirm that these structures are promising as applied to the frequency multiplication. The effect of frequency multiplication is demonstrated experimentally at low frequencies

Ultrafast All-Optical Switching In Semiconductor Nonlinear Directional-Couplers At Half The Band-Gap

Efficient ultrafast all-optical switching in nonlinear directional couplers made of AlGaAs and AlGaAs/GaAs quantum wells near half the band gap is reported. The switching is limited by multiphoton absorption which is dominated by three-photon absorption in this spectral range. The three-photon absorption in the quantum well nonlinear directional coupler is stronger than that of bulk AlGaAs. Autocorrelations of the output pulses in the bar and cross states confirm pulse breakup through nonlinear coupling, and illustrate the effects of multiphoton absorption. All sets of experimental data are fitted well by a theoretical model

Hot probe measurements on neutron irradiated, isotope enriched ZnO nanorods

We report on neutron transmutation doping (NTD) of isotopically (64Zn) enriched ZnO nanorods to produce material with holes as the majority mobile carrier. Nanorods of ZnO enriched with 64Zn were synthesised and the abundance of 64Zn in these samples is ∼ 71%, compared to the natural abundance of ∼ 49 %. The enriched material was irradiated with thermal neutrons which converts some 64Zn to 65Zn. The 65Zn decays to 65Cu with a half-life of 244 days and the Cu can act as an acceptor dopant. After 690 days, a hot probe technique was used to determine the majority charge carriers in non-irradiated and neutron irradiated nanorod samples. Non-irradiated samples were measured to be to have electrons as the majority mobile carrier and the irradiated samples were measured to have holes as the majority mobile carrier

Giant suppression of shot noise as signature of coherent transport in double barrier resonant diodes

Shot noise suppression in double barrier resonant tunnelling diodes with a Fano factor well below the value of 0.5 is theoretically predicted. This giant suppression is found to be a signature of the coherent transport regime and can occur near zero temperature as a consequence of the Pauli principle or above about 77 K as a consequence of long range Coulomb interaction. These predictions are validated by experimental data