7 research outputs found
Characterization of high-temperature PbTe p-n junctions prepared by thermal diffusion and by ion-implantation
We describe here the characteristics of two types of high-quality PbTe
p-n-junctions, prepared in this work: (1) by thermal diffusion of In4Te3 gas
(TDJ), and (2) by ion implantation (implanted junction, IJ) of In (In-IJ) and
Zn (Zn-IJ). The results, as presented here, demonstrate the high quality of
these PbTe diodes. Capacitance-voltage and current-voltage characteristics have
been measured. The measurements were carried out over a temperature range from
~ 10 K to ~ 180 K. The latter was the highest temperature, where the diode
still demonstrated rectifying properties. This maximum operating temperature is
higher than any of the earlier reported results.
The saturation current density, J0, in both diode types, was ~ 10^-5 A/cm2 at
80 K, while at 180 K J0 ~ 10^-1 A/cm2 in TDJ and ~ 1 A/cm2 in both
ion-implanted junctions. At 80 K the reverse current started to increase
markedly at a bias of ~ 400 mV for TDJ, and at ~550 mV for IJ. The ideality
factor n was about 1.5-2 for both diode types at 80 K. The analysis of the C-V
plots shows that the junctions in both diode types are linearly graded. The
analysis of the C-V plots allows also determining the height of the junction
barrier, the concentrations and the concentration gradient of the impurities,
and the temperature dependence of the static dielectric constant. The
zero-bias-resistance x area products (R0Ae) at 80 K are: 850 OHMcm2 for TDJ,
250 OHMcm2 for In-IJ, and ~ 80 OHMcm2 for Zn-IJ, while at 180 K R0Ae ~ 0.38
OHMcm2 for TDJ, and ~ 0.1 OHMcm2 for IJ. The estimated detectivity is: D* ~
10^10 cmHz^(1/2)/W up to T=140 K, determined mainly by background radiation,
while at T=180 K, D* decreases to 108-107 cmHz^(1/2)/W, and is determined by
the Johnson noise
Percolation model for the superconductor-insulator transition in granular films
We study the temperature dependence of the superconductor-insulator
transition in granular superconductors. Empirically, these systems are
characterized by very broad resistance tails, which depend exponentially on the
temperature, and the normal state resistance. We model these systems by a
two-dimensional random resistor percolation networks in which the resistance
between two grains is governed either by Josephson junction coupling or by
quasi particle tunneling. Our numerical simulations as well as an effective
medium evaluation explain the experimental results over a wide range of
temperatures and resistances. Using effective medium approximation we find an
analytical expression for the effective resistance of the system and the value
of the critical resistance separating conducting from insulating branches.Comment: 4 pages, 2 figure