New approach to the design of Schottky barrier diodes for THz mixers

Near-ideal GaAs Schottky barrier diodes especially designed for mixing applications in the THz frequency range are presented. A diode fabrication process for submicron diodes with near-ideal electrical and noise characteristics is described. This process is based on the electrolytic pulse etching of GaAs in combination with an in-situ platinum plating for the formation of the Schottky contacts. Schottky barrier diodes with a diameter of 1 micron fabricated by the process have already shown excellent results in a 650 GHz waveguide mixer at room temperature. A conversion loss of 7.5 dB and a mixer noise temperature of less than 2000 K have been obtained at an intermediate frequency of 4 GHz. The optimization of the diode structure and the technology was possible due to the development of a generalized Schottky barrier diode model which is valid also at high current densities. The common diode design and optimization is discussed on the basis of the classical theory. However, the conventional fomulas are valid only in a limited forward bias range corresponding to currents much smaller than the operating currents under submillimeter mixing conditions. The generalized new model takes into account not only the phenomena occurring at the junction such as current dependent recombination and drift/diffusion velocities, but also mobility and electron temperature variations in the undepleted epi-layer. Calculated diode I/V and noise characteristics are in excellent agreement with the measured values. Thus, the model offers the possibility of optimizing the diode structure and predicting the diode performance under mixing conditions at THz frequencies

Отголоски язычества в декоре уральской избы

Samples of a wooden carving of the XIX–XX centuries on Central Ural Mountains comprise basic symbolics of mythology of ancient Slavs. In the traditional dwelling elements of a mythological picture of the world are obviously traced. The myth represents model of a macrocosmos and the microcosm entered in it — the person. The traditional dwelling both in practical, and in symbolical aspect personifies the same relations. The mythological symbolics used as a decor had to fix, on the one hand, symbolical value of the house as center, Space as vital space of a sort, family, separately taken person. On the other hand, a number of symbols had to indicate specific preferences of some certain values of life of the owner of the house which, in turn, were caused by practical activity.Образцы деревянной резьбы XIX–XX веков на Урале представляют собой основную символику мифологии древних славян. Наиболее явно рудименты языческих культов были представлены в традиционном оформлении крестьянской избы. В избе прослеживаются элементы мифологической картины мира. Дом рассматривается и как центр пространства, и как элемент мироздания. Отсюда идет использование оберегающих знаков, защищающих проживающих в избе от разного вмешательства, идущего из внешнего мира