No abstract

An original approach to selective doping of Si by antimony (Sb) in molecular beam epitaxy (MBE) is proposed and verified experimentally. This approach is based on controllable utilization of the effect of Sb segregation. In particular, the sharp dependence of Sb segregation on growth temperature in the range of 300-550 C is exploited. The growth temperature variations between the kinetically limited and maximum segregation regimes are suggested to be utilized in order to obtain selectively doped structures with abrupt doping profiles. It is demonstrated that the proposed technique allows formation of selectively doped Si:Sb layers, including delta (d-)doped layers in which Sb concentrations can be varied from 5 Â 10 15 to 10 20 cm À3. The obtained doped structures are shown to have a high crystalline quality and the short-term growth interruptions, which are needed to change the substrate temperature, do not lead to any significant accumulation of background impurities in grown samples. Realization of the proposed approach requires neither too low (<300 C), nor too high (>600 C) growth temperatures or any special equipment for the MBE machines. V

The principles of construction of millimeter wave detectors based on low-barrier Schottky diodes and planar antennas are discussed. The modified planar slot antenna with low beam spillover at the resonant frequency of 94 GHz has been developed. Experiments have been carried out to investigate detecting characteristics of the diodes with differential contact resistances R j ¼ 1 Ä 1000 kΩ at zero bias. Experimental data are well correspond to calculations in a simple model of detector. At R j ¼ 20 Ä 100 k Ω the maximum of rf-todc voltage sensitivity -more than 10000 V/W -is obtained. At lower values of R j ¼ 2 Ä 6 k Ω a better noise equivalent power (NEP), around 10 −12 W Hz −1/2 , is predicted.

We develop the design and technology principles for manufacturing sensitive microwave detectors based on Schottky diodes with reduced effective barrier height (up to 0.2-0.3 eV). A family of diodes and broadband detectors on their basis with sensitivity from 1000 to 5000 V/W and threshold power 10 −11 W · Hz −1/2 in the short-wavelength part of the millimeter waveband, operated without constant bias is produced. A fairly exact description of the detector characteristics is obtained from calculations by a simple detecting model allowing for the capacitance and series spreading resistance of the diode. This method allows us to obtain a reliable dependence of the capacitance (reactive impedance) on the voltage for diodes working in the detection mode in the short-wave part of millimeter wavelengths.

Carbon was implanted into GaAs at the energy of 1 MeV with doses between 1×1013 and 2×1015 cm−2 at temperatures of 80 K, nominal room temperature (RT), and 300 °C. A markedly higher electrical activation was obtained in the samples implanted at 80 K compared to those implanted at RT or 300 °C, attaining a maximum hole concentration of 2×1019 cm−3. The redistribution of the C profile during rapid thermal annealing at temperatures from 700 to 950 °C for 10 s was found negligible, independently of the implantation temperature. Similar improvements in the electrical properties were also verified in samples implanted at 80 K with a lower energy of 60 keV. We consider that despite the light mass of C ions, the reduced dynamic annealing at 80 K allows the accumulation of an abundance of As vacancies, which assist the C activation as a p-type dopant.