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Torkhov N.A.,Research Institute of Semiconductor Devices | Novikov V.A.,Tomsk State University
Semiconductors | Year: 2011

During the formation of the metal-semiconductor contact with a Schottky barrier (as a gold film on the p- or n-type gallium arsenide surface), an electric field El built into the electric contact is induced, which propagates around the contact to the distance l (halo) tens of times larger than space-charge region sizes. This field reduces the electrostatic potential of the φAu contact by a significant value φ*. In the general case, the halo size l and the decrease φ* in the electrostatic potential are controlled by the charge value and sign in the space-charge region, which depend on the contact diameter D, semiconductor concentration and conductivity type. For Au/n-GaAs Schottky-barrier contacts, a decrease in D results in the increasing role of periphery, which manifests itself in increasing φ* and decreasing φAu and l. For Au/p-GaAs contacts, a decrease in D results in the decreasing effect of periphery, which appears in decreasing φ* and increasing φAu and l. The absence of the space-charge region in metal-insulator-semiconductor contacts results in the fact that the halo size l and φ* are independent of their diameters. © 2011 Pleiades Publishing, Ltd. Source


Torkhov N.A.,Research Institute of Semiconductor Devices
Semiconductors | Year: 2011

Electrical interaction between metal-semiconductor contacts combined in a diode matrix with a Schottky barrier manifests itself in an appreciable variation in their surface potentials and static current-volt-characteristics. The necessary condition for appearance of electrical interaction between such contacts consists in the presence of a peripheral electric field (a halo) around them; this field propagates to a fairly large distances (>30 μm). The sufficient condition is the presence of regions where the above halos overlap. It has been shown that variation in the surface potential and the current-voltage characteristics of contacts occurs under the effect of the intrinsic electric field of the contact's periphery and also under the effect of an electric field at matrix periphery; the latter field is formed as a result of superposition of electric fields of halos which form its contacts. The degree of the corresponding effect is governed by the distance between contacts and by the total charge of the space charge regions for all contacts of the matrix: their number, sizes (diameter D i, j), concentration of doping impurities in the semiconductor N D, and physical nature of a metal-semiconductor system with a Schottky barrier (with the barrier height φ b). It is established that bringing the contacts closer leads to a relative decrease in the threshold value of the "dead" zone in the forward current-voltage characteristics, an increase in the effective height of the barrier, and an insignificant increase in the nonideality factor. An increase in the total area of contacts (a total electric charge in the space charge region) in the matrix brings about an increase in the threshold value of the "dead" zone, a relative decrease in the effective barrier height, and an insignificant increase in the ideality factor. © 2011 Pleiades Publishing, Ltd. Source


Torkhov N.A.,Research Institute of Semiconductor Devices
Semiconductors | Year: 2011

It is shown that changes in device characteristics and an increase in the light-to-electrical energy conversion efficiency in metal-semiconductor Schottky barrier contacts are associated with a peripheral electric field built into the contact. For contacts with longer perimeters, variations in device characteristics and the light-to-electrical energy conversion efficiency are significantly larger. Since the photovoltage and peripheral electric fields in the contact region are codirected with the intrinsic electric field of the space-charge region, contact illumination results in a larger increase in the "dead" zone in forward portions of current-voltage characteristics, a larger decrease in the effective Schottky barrier height, and an increase in the field electron emission. An increase in the reverse field emission under photovoltage leads to an increase in the recombination current in the space-charge region, which provides dc photocurrent flow in the circuit. © 2011 Pleiades Publishing, Ltd. Source


Torkhov N.A.,Research Institute of Semiconductor Devices
Semiconductors | Year: 2010

Kelvin probe atomic-force microscopy of the electrostatic surface potential of gold Schottky contacts on n-GaAs showed that there is an extended transition area (halo) (tens of micrometers) around contacts in which the surface potential varies from the n-GaAs free surface potential to the gold contact surface potential. The contact potential and its distribution in the surrounding halo are controlled by the contact structure. The study of spreading currents showed that there is a high-conductance area (periphery) around the contact perimeter due to strong electric fields of the halo, which causes leakage currents. The conductivity of the main contact area is caused by 100- to 200-nm local areas with higher and lower conducting abilities. Mesa formation around contacts causes a decrease in the work function, a decrease in the halo extent and electric field strength, which is accompanied by spreading and decreasing of the peripheral area conductance. This results in disappearance of leakage currents and a decrease in the ideality index. In contrast, protection of the peripheral area by a SiO2 insulating film 0. 5 μm thick increases the work function, which is accompanied by the formation of potential lobes around the contact in two mutually perpendicular crystallographic directions. A stronger penetration of halo electric fields into the contact area results in an increase in the ideality index and disappearance of high-conductance peripheral area and leakage currents. The difference between the electrical properties of the periphery, gold grains, and their boundaries controls the contact switching mechanism when applying forward or reverse biases. © 2010 Pleiades Publishing, Ltd. Source


Ayzenshtat G.I.,Tomsk National Research University | Yushchenko A.Y.,Research Institute of Semiconductor Devices
Instruments and Experimental Techniques | Year: 2015

It was determined that the forward loss resistance as a function of the radius of the active region of typical microwave p-i-n diodes depends on the ratio of the square of the ambipolar-diffusion length to the square of the radius of the diode active region. Based on this regularity, a method was developed that provides simple determination of the ambipolar-diffusion length and the carrier lifetime. © 2015, Pleiades Publishing, Inc. Source

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