5 research outputs found
Electric Field Effect Analysis of Thin PbTe films on high-epsilon SrTiO3 Substrate
Thin PbTe films (thickness 500 - 600 angstrom), deposited on SrTiO3, have
been investigated by electric field effect (EFE). The high resistivity of such
thin films warrants a high sensitivity of the EFE method. The SrTiO3 substrate
serves as the dielectric layer in the Gate-Dielectric-PbTe structure. Due to
the large dielectric constant of SrTiO3, particularly at low temperatures, the
electric displacement D in the film reaches the high value of about 10^8 V/cm,
and the EFE introduced charge into the PbTe film amounts to ~ 8 microC/cm2. The
high D permits to measure the EFE resistance and Hall constant over a wide
region of D, revealing the characteristic features of their D-dependence. An
appropriate theoretical model has been formulated, showing that, for such
films, one can measure the dependence of the Fermi level on D. In fact, we
demonstrate that shifting the Fermi level across the gap by varying D, the
density-of-states of the in-gape states can be mapped out. Our results show,
that the PbTe layers studied, possess a mobility gap exceeding the gap of bulk
PbTe.Comment: 27 pages, 12 figure
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