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The electroluminescence (EL) properties of the [Gd.sup.3+] ultraviolet (UV) luminescent centers in Si[O.sub.2] metal-oxide-semiconductor light emitting devices (MOSLEDs) are investigated. The strong EL quenching related to a negative charge trapping around the optically active [Gd.sup.3+] luminescent centers is observed during excitation by hot electron injection, suggesting different methods for improving the EL stability of rare-earth doped MOSLEDs.

An experiment is conducted to examine coherent and incoherent transport of charge carriers in a p-i-n diode-embedded InGaAsP/InGaAsP superlattice using time-resolved differential electroabsorption spectroscopy. Results show that the dephasing and frequency of Bloch oscillations are affected by carrier sweep-out and sub-picosecond field screening. Moreover, coherent current oscillations increase relative to the amount of electric field applied.

Bright green electroluminescence with luminance up to 2800 cd/m2 is reported from indium-tin-oxide/SiO2:Tb/Si metal-oxide-semiconductor devices. The SiO2:Tb3+ gate oxide was prepared by thermal oxidation followed by Tb+ implantation. Electroluminescence and photoluminescence properties were studied with variations of the Tb3+ ion concentration and the annealing temperature. The optimized device shows a high external quantum efficiency of 16% and a luminous efficiency of 2.1 lm/W. The excitation processes of the strong green electroluminescence are attributed to the impact excitation of the Tb3+ luminescent centers by hot electrons and the subsequent crossrelaxation from 5D3 to 5D4 energy levels. Light-emitting devices with micrometer size fabricated by the standard metal-oxide-semiconductor technology are demonstrated. [ABSTRACT FROM AUTHOR]

Intersubband optical transitions at short wavelengths in strain-compensated In0.70Ga0.30As—AlAs double quantum wells are investigated by means of mid-infrared absorption. Trade-offs between achieving a high transition energy and a large oscillator strength of the two highest-energy intersubband transitions using our strain-compensation approach are analyzed as a function of the widths of the two wells. Two design strategies leading to relatively strong intersubband optical transitions at 800 meV, 1.55 μm, are described and the corresponding structures grown using gas-source molecular-beam epitaxy on (001)InP are investigated. The strongest intersubband transitions obtained experimentally are generally between 300 and 600 meV, 2–4 μm. Significant oscillator strength, however, also extends out to 800 meV, 1.55 μm. [ABSTRACT FROM AUTHOR]

A laser based picosecond ultrasound technique is used to study the doping profile in different n-doped GaAs homoepitaxial structures grown by molecular beam epitaxy. The picosecond ultrasound is found to be good tool to detect doping profile with doping densities of the order of [10.sup.18] [cm.sup.-3] based on a different sensitivity function for coherent strain pulse in the doped and undoped regions.

Bright green elelctroluminescence with luminance up to 2800 cd/m(sub 2) is reported from indium-tin-oxide/SiO2: Tb/Si metal-oxide-semiconductor devices. Electroluminescence and photoluminescence properties were studied with variations of the Tb(super 3+) ion concentration and the annealing temperature and several approaches for gaining light from silicon-based systems is reported with the prospect of sufficient electroluminescence efficiency.

The picosecond dynamics of electrons in a doped GaAs/AlGaAs superlattice have been investigated by pump-probe experiments using an infrared free-electron laser. We observe a fast bleaching of the interminiband absorption followed by thermalization and a slower cooling component. The latter can lead to a positive or negative transmission change, resulting from the temperature dependence of the linear absorption spectrum at the respective wavelength. We show that the superlattice in contrast to quantum wells provides a unique picosecond thermometer for the electron temperature based on the dependence of the absorption on the electron distribution function. [ABSTRACT FROM AUTHOR]

We report on the terahertz (THz) emission from GaSb surfaces with modified surface stochiometry. While very weak emission is observed from virgin GaSb wafers, the emission is significantly increased by a single thermal treatment of the wafers. Optimum emission is observed for 500 °C thermal annealing. The reason for the THz emission is a surface electric field induced by thermal decomposition of the surface, as corroborated by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

We have studied intersubband absorption in strain compensated In[SUBx[Ga[SUB1-x]As/AlAs/In[SUBy]Al[SUB1-y]Asmultiple quantum wells and superlattices grown on InP. X-ray diffraction shows that the layers are pseudomorphically strained and exhibit slight compositional grading of the interfaces. Owing to the high AlAs barriers, the intersubband absorption can be tailored to wavelengths shorter than 2 mm. In some samples, a small, but non-negligible absorption is also observed with s-polarized light. [ABSTRACT FROM AUTHOR]