Alloyed, Thin-Base Diode Capacitors for Parametric Amplification

Abstract

The design of double alloyed, thin-base diode capacitors for parametric amplification is described which indicates that capacitors with maximum Q's well in excess of 200 at 1 kmc and capacitive swings in excess of 15 are obtainable. The high Q's resulting from the type of fabrication and the small base thickness used; the large capacitive swing resulting from the abrupt p+n junction created. Three figures of merit are defined and evaluated: (1) an over-all device figure, FD, proportional to the product of the maximum Q and capacitance ratio evaluated in terms of material parameters, degree of base doping, and geometry factors; (2) a Q factor, FQ, proportional to just the capacitor Q; and (3) a material factor, FM, by which different materials used for fabrication can be compared. Fixing the choice of material (with germanium shown to be superior to silicon for this purpose) and achieving the best geometry, FD and FQ are examined as a function of doping. It is shown that FQ is nearly constant over the entire practical range of doping while FD, because of the capacitive swing, increases substantially with lighter doping. Results are presented for units with all soldered connections (no pressure contacts) fabricated from double alloyed pellets with a p+nn+ structure. To date, diode capacitors with maximum Q's in excess of 200 at 1 kmc and with capacitive swings in excess of 10 have been made. It is anticipated that this fabrication process will yield Q's in excess of 500 at 1 kmc with closer alloying control.

A Vapor-Grown Variable Capacitance Diode

“…It should be pointed out that although Eqs, (1)(2)(3)(4) and (1)(2)(3)(4)(5) are valid for regions where a plot of log C vs log (VD-V) gives straight lines, the converse is not true. A particular power law relationship of Nn-N A with distance, extends nearer the junction than the corresponding power law relationship of capacitance.…”

“…From Eq. (1)(2)(3)(4)(5), it is seen that there is no upper limit for IX if the variation in N D -N A ean be adjusted appropriately. Values of IX greater than or equal to 1, however, are not possible in the limit as V ()-V approaches zero, since then an infinite amount of charge is contained in an infinitesimal region, i.e., Q= l°qA(ND~NA)dX~et:) fora;::'1.…”

A Carbon Nanotube-based NEMS Parametric Amplifier for Enhanced Radio Wave Detection and Electronic Signal Amplification

“…is modulated at a sub-multiple of twice the resonance frequency, 2ω 0 /n, to produce amplification in the response of the system. Parametric amplifiers have generated sustained interest because their operational noise can approach the quantum-limit 3,4 and several implementations of phenomenon have been demonstrated in electronic systems using varactors 5 and Josephson junctions 6 , optical systems using nonlinear materials 7 , and in electromechanical systems 8 . In this paper, we explore the parametric amplification of mechanical oscillations in a suspended carbon nanotube resonator.…”