A simple on-line interactive computing methodology for determining static parameters of large-signal semiconductor models is described. The procedure makes use of: (1) an automatic data collection scheme, (2) a single search, three-parameter optimization method for computing diode parameters, and (3) a partitioning scheme to separate the defining transistor equations into two single search, three-parameter problems which are solved by the diode optimization method described in (2).
The method is described by means of the CIRCUS diode and transistor models, and is compared experimentally with Sokal's method [1,2]. The new approach is shown to be superior. 相似文献
Epitaxial growth on GaN bulk single crystal substrates sets new standards in GaN material quality. The outstanding properties provide insights into fundamental material parameters (e.g. lattice constants, exciton binding energies, etc.) with a precision not obtainable from heteroepitaxial growth on sapphire or SiC. With metalorganic vapor phase epitaxy (MOVPE) we realized unstrained GaN layers with dislocation densities about six orders of magnitude lower than in heteroepitaxy. By the use of dry etching techniques for surface preparation, an important improvement of crystal quality is achieved. Those layers reveal an exceptional optical quality as determined by a reduction of the low-temperature photoluminescence (PL) linewidth from 5 meV to 0.1 meV and a reduced X-ray diffraction (XRD) rocking curve width from 400 to 20 arcsec. As a consequence of the narrow PL linewidths, new features as, e. g. a fivefold fine structure of the donor-bound exciton line at 3.471 eV was detected. Additionally, all three free excitons as well as their excited states are visible in PL at 2 K.
Dry etching techniques for surface preparation allow morphologies of the layers suitable for device applications. We report on InGaN/GaN multi-quantum-well (MQW)_ structures as well as GaN pn- and InGaN/GaN double heterostructure light emitting diodes (LEDs) on GaN bulk single crystal substrates. Those LEDs are twice as bright as their counterparts grown on sapphire. In addition they reveal an improved high power characteristics, which is attributed to an enhanced crystal quality and an increased p-doping. 相似文献
Dramatic changes in the valence band of graphite, resulting from the insertion of bromine between the layers, are directly measurable using the ESCA technique. 相似文献
Measurements of magnetic susceptibility in the temperature range 4.2–300 K were made on polycrystalline samples of the (AgIn)1 - zMn2zTe2 and (CuIn)1 - zMn2zTe2 alloys, and the data used to give values of spin-glass transition te mperature Tg and Curie-Weiss paramagnetic temperature θ. For any sample for which the X-ray powder photograph indicated an apparently single phase condition, either zinc-blende or chalcopyrite, the susceptibility data could show up to three separate Tg values. These different magnetic conditions are attributed to crystallographic ordering of the Mn ions on the chalcopyrite and zinc-blende lattices, the three observed Tg values corresponding to disordered zinc-blende, ordered zinc-blende and ordered chalcopyrite. The value of θ obtained from the 1/χ vs. T plot is shown to be a weighted mean of the separate values of θ for the phases present. The relative sizes of the Tg peaks and the values of θ for any given sample gives an indication of the amount of each phase present. These amounts were varied by using different methods of heat treatment and it was shown that the magnetic behaviour was consistent with the T(z) phase diagram for the two alloy systems. 相似文献