We have proposed and experimentally verified a local method ofmicrowave resonant spectroscopy of semiconductors. The microwave circuit ofthe spectrometer based on the Cascade Microtech probe station is equippedwith a coaxial resonator of special geometry. As result, the measurementaccuracy of the previously developed volt-impedance spectroscopy method wasgreatly increased. A technique for spectrometer calibration and resonantmeasurements of the complex impedance of the probe-sample system has beendeveloped. We have measured the impedance of test structures with Schottkycontacts of 30-60 μm in diameter on a single-crystal GaAs wafer at severaldiscrete frequencies in the range of 50-250 MHz . The nontrivial resistiveproperties of the structures are studied, which consist of the excessresistance that is 1-2 orders higher than the spreading resistance for thealternating current in the unperturbed region of the semiconductor. Thediscovered effect is presumably associated with the a.c. charge modulationon deep levels of the semiconductor. A model calculation of the impedancespectrum has been performed, which demonstrates a good agreement with theexperimental spectra. Keywords: Microwave microscope, near field, probe, resonator, impedance, semiconductor.\

Microwave voltage-impedance spectroscopy is used to study a semiconductor structure in the form of a doped n-GaAs film grown on a conducting n+-GaAs substrate with a buffer sublayer. A system of concentric barrier contacts is formed on the structure surface. A technique has been developed for measuring complex impedance spectrum Z(f,U) of the sample as a function of DC bias voltage U. Spectra Z(f,U) were measured using a Cascade Microtech probe station in the frequency range 0.01 – 40 GHz with a lateral resolution of 15 – 30 μm at U = 0 – 10 V. The main electrophysical characteristics of a semiconductor film were determined from the spectra: type, concentration and mobility of free charge carriers, electrical conductivity. An excess resistance was found in the range f = 0.1 – 20 GHz. This effect is interpreted as the deep states (traps) recharging for two types of traps – low-frequency l and high-frequency h with characteristic time τl = 10^(-9) s, τh = 4.2∙10^(-11) s. A model description is proposed that explains the characteristic shape of the trap resistance spectrum, its dependence on the contact area and voltage U.

We have proposed and experimentally verified a local method of microwave resonant spectroscopy of semiconductors. The microwave circuit of the spectrometer based on the Cascade Microtech probe station is equipped with a coaxial resonator of special geometry. As result, the measurement accuracy of the previously developed volt-impedance spectroscopy method was greatly increased. A technique for spectrometer calibration and resonant measurements of the complex impedance of the probe-sample system has been developed. We have measured the impedance of test structures with Schottky contacts of 30 - 60 μm in diameter on a single-crystal GaAs wafer at several discrete frequencies in the range of 50 - 250 MHz. The nontrivial resistive properties of the structures are studied, which consist of the excess resistance that is 1–2 orders higher than the spreading resistance for the alternating current in the unperturbed region of the semiconductor. The discovered effect is presumably associated with the a.c. charge modulation on deep levels of the semiconductor. A model calculation of the impedance spectrum has been performed, which demonstrates a good agreement with the experimental spectra.

The influence of thermal annealing on the transport properties of Ti/AlGaN/GaN low-barrier Mott diodes with near-surface polarization-induced δ-doping has been studied. It is shown that annealing provides additional possibilities for controlling the effective barrier height of diodes, improving and fine-tuning their transport characteristics. Thermal annealing can be used to fabricate low-barrier diodes designed to operate at high temperatures.

Theoretical analysis of the degradation of the current–voltage characteristic and transient ionization processes occurring in a low-barrier uncooled GaAs Mott diode under the action of heavy ions from outer space and laser pulses simulating them is carried out. The response of the diode to the action of an arsenic ion with an energy of 200 MeV, which corresponds to a linear energy transfer of 26 MeV cm 2 /mg, is compared with the response to the action of femtosecond optical-radiation pulses with a duration of 10 fs at wavelengths of 870 and 670 nm.

All-epitaxial Al/AlxGa1−xN/GaN low-barrier Schottky diodes with different x compositions were fabricated in the single process of molecular-beam epitaxy. A decrease in the effective barrier height is achieved by polarization-induced δ-doping of the AlxGa1−xN/GaN heterojunction. At zero bias, the diodes have high values of ampere-watt sensitivity (7 A/W) with a low specific value of differential resistance (5 × 10−4 Ω⋅cm2) and retain non-linear properties when the resistance decreases to 10−4 Ω⋅cm2. The fundamental importance of the absence of impurities, oxides, and structural defects at the metal–semiconductor interface for effective control of the transport properties of diodes is demonstrated.

The influence of thermal annealing on the transport properties of Ti/AlGaN/GaN low-barrier Mott diodes with near-surface polarization-induced delta-doping has been studied. It is shown that annealing provides additional possibilities for controlling the effective barrier height of diodes, improving and fine-tuning their transport characteristics. Thermal annealing can be used to fabricate low-barrier diodes designed to operate at high temperatures. Keywords: low-barrier diode, GaN, transport properties, thermal annealing.

Transient ionization processes occurring in a low-barrier GaAs Mott diode under the influence of heavy charged particles from outer space and laser pulses that imitate such particles are analyzed theoretically. The response of a diode to the influence of an As + ion with an energy of 200 MeV, which corresponds to a linear energy transfer of 26 MeV cm 2 /mg, is compared with the response to the influence of optical radiation pulses of various durations (10–1000 fs) with a photon energy exceeding the band gap of GaAs.

A theoretical analysis of transient ionization processes occurring in a low-barrier GaAs Mott diode under the influence of space radiation high energy charged particles and simulating pulsed laser radiation is carried out. The diode response to the As+ ion action with an energy of 200 MeV, corresponding to a linear energy transfer of 26 MeV cm2/mg, is compared with the response to the femtosecond pulses optical radiation action of various durations (10-1000 fs) and photon energies exceeding the GaAs band gap.

A theoretical analysis of the degradation of the current-voltage characteristic and transient ionization processes occurring in a low-barrier uncooled GaAs Mott diode under the action of heavy ions of outer space and laser pulses simulating them is carried out. The response of the diode to the action of an arsenic ion with an energy of 200 MeV, corresponding to a linear energy transfer of 26 MeV∙cm2/mg, is compared with the response to the action of femtosecond pulses of optical radiation with a duration of 10 fs with a wavelength of 870 nm and 670 nm.

The previously proposed technique of microwave volt–impedance spectroscopy of semiconductors has been experimentally verified. The technique allows one to determine the local values of electrical parameters of a semiconductor. The investigations have been carried out on a homogeneous single-crystal GaAs wafer with a system of concentric antennas formed on the top of it. The resolution is determined by the antenna central disk diameter, which has been 12, 27, and 57 μm. A dc bias voltage of 0 V ≤ U ≤ 5 V has been applied between antenna contact pads. The complex Z(f, U) impedance spectrum of each antenna has been measured on a Cascade Microtech probe station in the frequency range of f = 0.1–10 GHz. The electrical characteristics of the semiconductor have been determined from the Z(f, U) spectra by solving the inverse problem. The n-type of the semiconductor has been established, and the contact potential difference at the interface with a metal has been determined. The local values of electron density, mobility and electrical conductivity have been found have been found. The four-point probe Hall effect measurements of the surface-averaged values of the same parameters have shown good agreement of the results for the investigated homogeneous wafer.

We have tested experimentally the proposed method of microwave volt-impedance spectroscopy of semiconductors. The method allows to determine the local values of the semiconductor electrophysical parameters. The studies were performed on a homogeneous single-crystal GaAs wafer with a concentric antenna system formed on its surface. The resolution is determined by the diameter of the antenna central disk, which was amounted a = 12, 27, 57 μm. A constant bias voltage of 0 ≤ U ≤ 5 V was applied between the contact pads of the antennas. The complex impedance spectrum Z (f, U) of each antenna was measured using a Cascade Microtech probe station in the frequency range f = 0.1 - 10 GHz. The electrophysical characteristics of the semiconductor were determined from Z(f, U) spectra by the inverse problem solving. We have established the n-type for our semiconductor and determined the electrical potential difference on the metal-semiconductor interface. We have found as well the electron concentration, mobility and conductivity. Measurements of the same parameters by Hall four-probe method (giving the surface averaging) showed good mutual agreement of the results for the homogeneous sample under study.

The possibility of a controlled decrease in the effective height of the Schottky (Mott) barrier to the AlGaN/GaN (Ga-face polarity) heterostructure due to the modification of the shape of the barrier by the electric field of the polarization charge arising in the plane of the heterojunction because of the jump in electric polarization is experimentally shown. A decrease in the effective barrier height is related to an increase in the role of electron tunneling through the barrier. The effective barrier height can be controlled by varying the thickness and chemical composition of the AlGaN layer and choosing the metal of the barrier contact. Test low-barrier Mott Ti/AlGaN/GaN diodes demonstrating high values of the ampere-watt sensitivity (9 A/W) for a low specific differential resistance (4 × 10–4 Ω⋅cm2) at zero bias have been manufactured.

An original low-barrier diode n+-InGaAs/AlGaAs/n+-GaAs heterostructure was developed and grown by metalorganic vapor phase epitaxy. Growth conditions are practically the same as were used in standard pseudomorphic high-electron-mobility transistor technology. Test diodes were made on the basis of the heterostructure and their transport properties were studied. For comparison with experimental results, the transport characteristics of diodes were simulated in the framework of the combined thermionic-emission/diffusion theory. A useful method for the microwave measurements of diodes on a wafer was employed, which allows one to determine all the main parameters of the equivalent diode circuit and their detection characteristics. The diodes have a high quadratic nonlinearity parameter value (> 20 V−1) and small specific values of differential resistance (10−4 Ω cm2) and capacitance (10−7 F/cm2) at zero bias. The prospects of using the developed heterostructure to create highly sensitive microwave radiation detectors are shown.

AbstractThe characteristics of millimeter-wavelength detectors based on planar Mott diodes with near-surface δ-doping operating without a constant bias are discussed. These detectors have a volt–watt sensitivity of ~1000 V/W with NEP ~ 10 pW/Hz^1/2 in the 150–250 GHz range. The obtained estimates reveal the possibility of an additional order-of-magnitude enhancement of the performance characteristics of detectors with smaller areas of the diode barrier contact.

The characteristics of millimeter-wavelength detectors based on planar Mott diodes with near-surface δ-doping operating without a constant bias are discussed. These detectors have a volt–watt sensitivity of ~1000 V/W with NEP ~ 10 pW/Hz1/2 in the 150–250 GHz range. The obtained estimates reveal the possibility of an additional order-of-magnitude enhancement of the performance characteristics of detectors with smaller areas of the diode barrier contact.

The first results on the development of an original power GaAs-based field-effect transistor with a vertical channel controlled by a p–n junction are presented. The main manufacturing feature is the use of two separate epitaxial growth processes when forming the transistor structure. The transistor part containing the drain, drift, and gate regions is grown by liquid-phase epitaxy. Metalorganic gas-phase epitaxy is used to form the channel and source regions.

The first results on the creation of an original power GaAs field-effect transistor with a vertical channel controlled by the p-n junction are presented. The main technological feature is the use of two separate processes of epitaxial growth in the formation of the transistor structure. The part of the transistor containing the drain, drift and gate areas is grown by liquid-phase epitaxy. The technology of organometallic gas-phase epitaxy is used to form the areas of the channel and the source.

The methods of impedance spectroscopy of (Al, In, Ga)As-based pHEMT heterostructures are developed using an LCR meter in the frequency range 0.1-2000 kHz and a vector network analyzer at higher frequencies of 0.01-3 GHz. These methods determine all the main parameters of the pHEMT heterostructures, including the threshold voltage, the channel resistance, the sheet density of electrons, and their mobility at operating biases.