Characteristics of diode temperature sensors which exhibit Mott conduction in low temperature region

Heavily doped silicon diodes of n⁺⁺-p⁺ type which exhibit the Mott temperature dependence of the forward current in a certain range of bias voltages and low temperatures have studied from the point of their use as temperature sensors. In the region of hopping conduction, the operating signal of diodes U (T) (U is a voltage drop across the diode during the passage of a constant current, T is the temperature) reproduces the Mott law (with opposite sign in the exponent), and the temperature sensitivity of such sensors after passing through a minimum (as the temperature is lowered) increases again up to the values typical of room temperatur

A new method of extraction of a p-n diode series resistance from I-V characteristics and its application to analysis of low-temperature conduction of the diode base

A new analytical method of extraction of a diode series resistance from current-voltage characteristics is proposed which takes into account dependence of the series resistance on voltage (or current). The method supposes a presence of linear section in the diode current-voltage characteristic plotted in semi-logarithmic scale. This method is applied here to experimental data for silicon diode in which series resistance is caused by freezing-out free current carriers into impurities at cryogenic temperatures. Character of dependence of the base resistance on electric field in the base layer determined in such way confirms hopping nature of silicon conduction under these conditions

Negative magnetoresistance of heavily doped silicon p-n junction

At the liquid helium temperature and under application of magnetic fields up to 9.4 T, a voltage drop across a silicon diode with metallic conductivity of the emitter and base has been measured under passing a constant forward current through the diode. Observed magnetoresistance of the diode is proved as a whole to be extremely small, negative at low fields and changing its sign when the field increases. In the positive region of the diode magnetoresistance, its field dependence is quadratic at first and then becomes close to the linear one. With increase in the current through the diode, the negative component of the diode magnetoresistance decreases, and the smaller its value, the more extended is the quadratic section and the shorter is the linear one. The results are interpreted as caused by hopping conduction over a system of electron “lakes” in the region of p-n junction

Smoothing cubic spline approximation of silicon diode temperature sensors thermometric characteristics

Shown in this paper is the efficiency of a smoothing cubic spline approximation for temperature response curves (TRC) of wide range silicon diode thermometers (SDTs). The offered calculation algorithm allows to describe TRC with a high accuracy and receive the interpolation tables with any temperature step. It allows essentially to expand SDT field of application

Effect of magnetic field on hysteretic characteristics of silicon diodes under conditions of low-temperature impurity breakdown

Effect of magnetic field (up to 14 T) on current-voltage characteristics of silicon n⁺ -p diodes which manifests hysteresis loops related with low-temperature impurity breakdown has been studied. With growth of magnetic field, the hysteresis loops are narrowed and decreased in amplitude and then disappear, but the breakdown continues in a soft form. Planar design of the diode has allowed separating the influence of magnetic field on mobility of the carriers executing impact ionization of the impurities and on the ionization energy itself. Theoretical analysis of the experimental data permitted us to determine the dependence of the ionization energy on the magnetic field. As in other investigated semiconductors, our results demonstrate the dependence of B¹/³ type. A model capable to explain qualitatively the mechanism of suppression of the hysteresis loops by magnetic field is proposed as well

Optimized calibration of cryogenic silicon thermodiodes

Shown in this paper is the efficiency of smoothing cubic spline approximation aimed at optimization of calibration of cryogenic silicon diode thermometers (SDTs). The proposed algorithm allows to significantly reduce time and material costs associated with calibration of SDTs

Nanocrystalline Ge films created by thermal vacuum deposition on GaAs substrates: structural and electric properties

The technique of thermal vacuum deposition of Ge onto GaAs substrates has been used for obtaining nanocrystalline Ge films. Nanocrystalline character of the films is confirmed by atomic force microscopy of their surface and by the data of Raman light scattering. The most probable size of the nanocrystallites forming the films decreases monotonically with decreasing their thickness. Electro conductivity of such the films proves to be high enough (1-10 Ohm·cm at room temperature) and has a character of variable range hopping conduction of Mott’s type. The hops, presumably, take place through the localized states connected with the grain boundaries

Some peculiarities of low temperature conductivity of silicon diodes

The forward current-voltage (I-V) characteristics of the n+-p silicon diodes, B-doped with impurity density p=2.1017 cm-3 and P-doped with impurity density n=2.1020 cm-3, have been investigated in the temperature range from 4.2 K to 293 K. The peculiarities of the low-temperature conductivity of diodes have been studied by the novel differential technique of experimental results treatment. The ranges of power-like and exponential dependencies of the I-V curves have been determined. Different physical mechanisms responsible for the formation of peculiarities of the low-temperature I-V characteristics have briefly been discussed

Non-ohmic Mott conductivity and thermometric characteristics of heavily doped silicon structures

We investigated I-V curves and thermometric characteristics of heavily doped p-silicon structures at liquid helium temperatures. The variable-range hopping conductivity is shown to occur in the structures studied. The obtained parameters of non-ohmic Mott conductivity and their temperature and electric field dependencies enabled us to explain the features in structure thermometric characteristics. It is shown that both height and position of the responsivity peak depend on the extent to which the hopping conductivity is non-ohmic. They are essentially determined by the density of states near the Fermi level

Peculiarities of injection phenomena in heavily doped silicon structures and development of radiation-resistant diode temperature sensors

To explain the experimental behaviour of differential characteristics (ideality factor, differential resistance) before and after radiation influence, a theoretical model of injection current flow mechanisms for the silicon diode temperature sensors (DTSs) is proposed. The observed nonmonotonic dependencies of the ideality factor on the current are described well by the influence of generation-recombination and drift current components to the diffusion current of the minority carriers. The developed model allowed to find characteristic lifetimes of the minority carriers in the base and in the space-charge region of the diode structure with heavily doped base and emitter regions. Investigations of electrophysical and metrological characteristics of the DTSs allowed to reveal such operating regimes that are characterised by minimal influence of radiation on the device thermometric characteristics