Article:Stone, M.R., Naftaly, M., Miles, R.E. et al. (2 more Abstract-We present experimental characterization of semilarge photoconductive emitters, including their electrical/photoconductive parameters and terahertz spectra. A range of emitters were studied and fabricated on both LT-GaAs and SI-GaAs, having a variety of electrode geometries. The spatial cone of terahertz radiation was defined. The dependencies of the photocurrent and the terahertz power on the bias voltage and the laser power were determined. A Fourier-transform interferometer is used to determine the terahertz spectra and to clarify the effects of the substrate and electrode geometry.
Room-temperature electroluminescence is reported from InAsSb multiple-quantum-well light-emitting diodes. The diodes exhibited emission in the mid-infrared peaking near 4 m. The spectral dependence on injection current at 4 K was investigated and two transitions were identified, centered at 4.05 and 3.50 m, which are associated with the eigenstates of the confined holes inside the quantum well. The use of an Sb predeposition and As flux surface exposure during epitaxial growth was observed to have a major effect on the electroluminescence output.
Continuous-wave terahertz ͑THz͒ radiation was generated by photomixing two modes of a titanium sapphire laser. The laser was induced to oscillate on two modes by placing a Fabry-Perot etalon in the laser resonator. The frequency of terahertz radiation, which was equal to the difference frequency of the two modes, was varied by adjusting the free spectral range ͑FSR͒ of the etalon. Photomixing was performed by logarithmic spiral antennas fabricated on low-temperature-grown GaAs; and the emitted THz radiation was characterized. The THz power, measured by a Golay cell, was 1 W at 0.3 THz and 0.7 W at 0.5 THz. The THz frequency, as determined by a Fourier transform interferometer, was seen to correspond to the etalon FSR. The current-voltage characteristics of photomixers were also determined, and photocurrent modulation was observed by the autocorrelation of the laser beam.
The liquid phase epitaxial growth of InAs 0.91 Sb 0.09 lattice-matched onto GaSb is reported for use in the active region of a mid-infrared light-emitting diode. Epitaxy was carried out from Sb-rich solution using Gd gettering to purify the material. The photoluminescence and electroluminescence emission spectra were studied over the temperature range 4-300 K using different excitation intensities. Interpretation of the resulting spectra revealed the existence of two acceptor levels with activation energies of 8 meV and 16 meV. Room temperature electroluminescence at 4.2 µm was readily obtained from homo-junction p-i-n diodes fabricated from this material. The temperature dependence of the electroluminescence was studied and the decrease in the radiative recombination coefficient was found to be primarily responsible for the luminescence quenching.
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