Effect of Atomic Layer Deposited HfO2 thin Film Interfacial Layer on the Electrical Properties of Au/Ti/n-GaAs Schottky Diode

The electrical properties of Au/Ti/HfO2/n-GaAs metal/insulating layer/semiconductor (MIS) contact structures were analyzed in detail by the help of capacitance-voltage (C-V) and conductance-voltage (G-V) measurements in the temperature range of 60–320 K. The HfO2 thin film layer was obtained by atomic layer deposition technique (ALD). The main electrical parameters such as ideality factor (n) and barrier height (ΦB0) were determined for Au/Ti/n-GaAs and Au/Ti/HfO2/n-GaAs diodes using current-voltage (I-V) measurement at 300 K. The values of these parameters are 1.07 and 0.77 eV for the reference (Au/Ti/n-GaAs) diode, and 1.30 and 0.94 eV for the Au/Ti/HfO2/n-GaAs MIS diode, respectively. An interfacial charge density value of Qss= 4.14x1012 Ccm− 2 for the MIS diode was calculated from the barrier height difference of ΔΦ=0.94-0.77=0.17 V. Depending on these results, the temperature dependent C-V and G-V plots of the device were also investigated. The series resistance (Rs), phase angle, the interface state density (Dit), the real impedance (Z') and imaginary impedance (Z'') were evaluated using admittance measurements. The C and G values increased, whereas (Z'') and Z decreased with increasing voltage at each temperature. An intersection point being independent of temperature in the G–V curves appeared at forward bias side (≈1.4 V), after this intersection point of the G–V plot, the G values decreased with increasing temperature at a given voltage. The intersection points in total (Z) versus V curves appeared at forward bias side (≈1.7 V). The Nyquist spectra was recorded for the MIS structure showing single semicircular arcs with different diameters depending on temperature.

Admittance of mis-structures based on pentacene with two-layer dielectric SiO2-Al2O3

Experimental studies of the admittance of MIS structures based on pentacene with a two-layer dielectric SiO2-Al2O3 and various materials for backward contact (Au, Al, In, Ag) have been carried out in a wide range of frequencies, temperatures, and biases. The concentration of holes in the organic film of pentacene, found from the capacitance-voltage characteristics, took rather high values (in the range (4-40)×1017 cm-3). The magnitude of the hysteresis of the electrophysical characteristics turned out to be minimal for structures with Ag and In reverse contacts. Significant hysteresis was found for structures with reverse contacts made of Au and Al at 300 K. For a structure with a reverse contact made of Al, with a forward voltage sweep in a weak accumulation mode, a maximum capacitance was observed, which can be associated with a recharge of the level of surface states at the interface between the inorganic insulator and pentacene. An equivalent circuit of a pentacene-based MIS structure is proposed, which allows one to calculate the frequency dependences of the impedance under various conditions. The values of the elements of the equivalent circuit are found at various biases and temperatures. For structures with backward contacts made of Au and Ag, maxima on the temperature dependence of the conductance associated with the recharge of bulk traps in the organic pentacene film were found.

Películas de SRO-HFCVD como dieléctrico en estructuras MIS y sus propiedades eléctricas

This paper presents the results obtained by the electrooptical characterization of a MIS structure built by depositing a film of an Indium Tin Oxide (ITO) on a Silicon Rich Oxide (SRO) film using the Chemical Vapor Deposition Hot Filament (HFCVD) system. The SROHFCVD films were deposited considering two hydrogen fluxes levels at 25 and 100 sccm, under these conditions we grow single and double films, both being heat treated at 1100 ° C to improve their optical and structural characteristics. Through of the techniques of Null Spectroscopy, XPS and Photoluminescence, it was possible to determine the thickness of the SRO films, quantify the silicon excess present in them and analyze their spectra. These films are used as the active layer in Metal-Insulating-Semiconductor (MIS) structures, such structures were electrically characterized through the I-V curves. From the result of these characterizations a comparison is made between the MIS structures with films virgin (V) and with ones heat-treated (T-T). Characterizations indicate that SRO-HFCVD films with T-T significantly modify the optical and electrical properties of MIS structures, which is promising for the design of integrated optical sensors.

Prototype of Nitro Compound Vapor and Trace Detector Based on a Capacitive MIS Sensor

A prototype of a nitro compound vapor and trace detector, which uses the pyrolysis method and a capacitive gas sensor based on the metal–insulator–semiconductor (MIS) structure type Pd–SiO2–Si, was developed and manufactured. It was experimentally established that the detection limit of trinitrotoluene trace for the detector prototype is 1 × 10−9 g, which corresponds to concentration from 10−11 g/cm3 to 10−12 g/cm3. The prototype had a response time of no more than 30 s. The possibility of further improving the characteristics of the prototype detector by reducing the overall dimensions and increasing the sensitivity of the MIS sensors is shown.