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In the present work, the influence of the deposition temperature of InSb films on semi-insulating GaAs(100) on their phase composition, crystal perfection and electrical properties was investigated. The InSb films of various extent of crystal perfection are formed by means of explosive thermal deposition of InSb on semi-insulating GaAs(100) substrates in the temperature range of 375–460 °C. X-ray diffraction analysis established that the films are heteroepitaxial. It is shown that an increase in the deposition temperature of InSb films from 375 to 460 °C leads to a change in the film surface roughness (Ra) from 3.4 to 19.1 nm. The Hall voltage sensitivity to the magnetic field of InSb films varies in the range of 500–1500 mV/T. The electron concentration (n) and mobility (μ) changes in the range of 2 ⋅ 1016 – 6 ⋅ 1016 cm–3, 10 ⋅ 103 – 21 ⋅ 103 cm2/(V ⋅ s). The formed InSb films on semi-insulating GaAs(100) substrate are of practical interest for the manufacture of highly sensitive miniature Hall devices.

This article presents results of research work aimed at manufacturing photoconductive semiconductor switches (PCSSs) based on semi-insulating (SI) gallium phosphide (GaP) and gallium nitride (GaN). Currently, the work is in progress to determine the optimal values of PCSS parameters. In this article, the parameters of the selected semiconductor materials used for making PCSSs, the device operation principle, and possible areas of use are presented. The paper demonstrates the construction of test PCSSs based on SI GaP and SI GaN and results of blocking characteristics measurements without the illumination, as well as with illumination with a small photon flux. Further research directions are presented also.

In the present work, effects of silicon negative ion implantation into semi-insulating gallium arsenide (GaAs) samples with fluences varying between 1 × 1015 and 4 × 1017 ions cm−2 at 100 k...

Two SiC crystals were grown using SiC source powder with different level of purity and then the effect of the purity of SiC source materials on the final electrical properties has been systematically observed. Furthermore, the variation of vanadium amount according to the growth direction of vanadium doped semi-insulated SiC single crystals has been investigated. The quality of SiC crystal grown using SiC source powder with higher purity was definitely better than SiC crystal with lower purity. SiC crystals having an average resistivity value of about 1×1010 Ωcm were successfully obtained. In the result of COREMA measurement, the use of high purity SiC powder was revealed to obtain wafers with better uniformity in resistivity value.

The present research was focused on the effect of porous graphite plate in TaC-coated crucible on crystal quality and resistivity of semi-insulating SiC crystals. Two SiC crystals grown with/without porous graphite plate in TaC-coated crucible were systematically compared. 6H-SiC polytype was obtained on both crystals regardless of porous graphite plate. The quality of SiC crystal grown using porous graphite plate placed in the TaC-coated crucible was slightly better than SiC crystal without porous graphite plate. SiC crystals having an average resistivity value of about 1×1010 Ωcm were obtained. In the result of COREMA measurement, the use of porous graphite plate tends to obtain wafers with better uniformity in resistivity value.

The electrical properties of AlGaN/GaN high electron mobility transistor structures with composite Fe-doped GaN/undoped GaN buffers grown on (1 1 0) Si substrates by ammonia molecular beam epitaxy were reported. Fe concentration in the range of 1017 cm−3 is sufficient to compensate the residual donors (

Temperature dependence of optical and electrooptical properties of the semi-insulating GaAs/AlGaAs multiple quantum well thin films was analyzed. The electroabsorption and thermoabsorption of the material in the excitonic resonance region were measured for the temperature range of 22 °C – 80 °C. The absorption edge shift due to the thermally induced change of the band gap width was observed as well as the decrease of the absorption in excitonic peaks.

V-doped semi-insulating (VDSI) SiC crystal is a promising substrate for high-frequency electronic devices achieved using GaN epitaxial films. However, V doping in a SiC crystal is difficult to control owing to the different sublimation temperatures of VC and SiC. The amount of V changes depending on the growth sequence, which has been a significant concern in VDSI SiC substrates in terms of wafer reliability. In this study, therefore, we aimed to synthesize a single source by vaporizing Si, C, and V under the same conditions to improve the doping issue in VDSI SiC. We synthesized V-doped SiC powder as the starting material for VDSI SiC substrate based on thermodynamic modeling, and the synthesized powder was used to grow a VDSI SiC crystal via physical vapor transport. Finally, considering the homogeneous V concentration in the grown crystal, the synthesized V-doped SiC was observed to be effective to grow VDSI SiC independent of the growth sequence.

The optical response of graphene on 6H-SiC was investigated by means of IR-reflectance measurements. Thereby, the anisotropy of the substrate is considered and its influence was studied by performing measurements with s- and p-polarized light. The anisotropy causes a splitting of the reststrahlen band in p-polarization, but does not affect spectra recorded with s-polarization. In both cases a thin film approximation was used to simulate the reflectance spectra. A model consisting of SiC, graphene and air enables the extraction of the graphene layer count.

The electrical characterization of high-purity semi-insulating 4H-SiC is carried out by means of current deep level transient spectroscopy (I-DLTS). Measurements are performed by employing either an electrical or optical pulse (below/above bandgap). The study performed on as-grown material, either annealed or oxidized, reveals the presence of six levels with ionization energies in the 0.4-1.3 eV range.

Alpha particle radiation detectors with planar double Schottky contacts (DSC) are directly fabricated on 5-μm-thick epitaxial semi-insulating (SI) GaN:Fe film with resistivity higher than 1 × 108 Ω ⋅cm. Under 10 V bias, the detector exhibits a low dark current of less than 5.0 × 10−11 A at room-temperature, which increases at higher temperatures. Linear behavior in the semi-log reverse current–voltage plot suggests that Poole–Frenkel emission is the dominant carrier leakage mechanism at high bias. Distinct double-peak characteristics are observed in the energy spectrum of alpha particles regardless of bias voltage. The energy resolution of the SI-GaN based detector is determined to be ∼ 8.6% at the deposited energy of 1.209 MeV with a charge collection efficiency of ∼ 81.7%. At a higher temperature of 90 °C, the measured full width at half maximum (FWHM) rises to 235 keV with no shift of energy peak position, which proves that the GaN detector has potential to work stably in high temperature environment. This study provides a possible route to fabricate the low cost GaN-based alpha particle detector with reasonable performance.

In this paper, a three-layer GaAs photoconductive semiconductor switch (GaAs PCSS) is designed to withstand high voltage from 20 to 35 kV. The maximum avalanche gain and minimum on-state resistance of GaAs PCSS are 1385 and 0.58 Ω, respectively, which are the highest values reported to date. Finally, the influence of the bias voltage on the avalanche stability is analyzed. The stability of the GaAs PCSS is evaluated and calculated. The results show that the jitter values at the bias voltages of 30 kV and 35 kV are 164.3 ps and 106.9 ps, respectively. This work provides guidance for the design of semiconductor switches with high voltage and high gain.

Electrical properties of semi-insulating CdTe-Cl crystals, grown by the vertical Bridgman and the travelling heater method, have been studied. It is found that the travelling heater method provides electron conductivity of the crystals, and the vertical Bridgman method - hole conductivity. Specific resistance of the samples is of (108-109) Ohm*cm at 300 K, and Hall mobility of the holes and electrons is of (45 - 55) cm2/V*sec. and (10 - 20) cm2/V*sec., respectively. Very low values of electron mobility and an exponential temperature dependence of µn are due to drift barriers with a height of εb ≈ 0,20 eV. Formation of the barriers is caused by the fluctuations of the potential relief resulting from the microheterogeneity of the defect-impurity system. Quasi-photochemical reactions that reduce electron mobility after photo-excitation have been observed in n-CdTe-Cl samples. In p-CdTe-Cl samples, neither drift barriers, nor quasi-photochemical reactions were detected. Key words: transport phenomena, scattering of charge carriers, cadmium telluride.

The internal charging effect is one of the most important factors threatening satellite’s life in the space environment. In this paper, a semi-insulating conformal coating is prepared on the circuit board surface by spray method aimed to eliminate the charging. The coating is composed of two layers. A polymethyl methacrylate (PMMA) base layer followed by top layer made of PMMA matrix polyaniline (PANI) composite with a surface resistivity of 1.49 × 1011 Ω. The structure and morphology of PANI were investigated by FTIR, XRD, and TEM. Anti-internal charge testing of PANI/PMMA conformal coating is performed by the internal charging simulation device. The results showed that the coating can prevent the discharge phenomenon effectively.

Comparative study of p-type 4H-SiC epitaxial layers grown simultaneously on two different 4H-SiC substrates, namely n-type and semi-insulating have been done by different structural, optical and electrical experimental techniques.

The optical properties of semi-insulating GaAs crystals subjected to multienergy hydrogen-ion implantation and treatment in a high-frequency electromagnetic field are studied in the infrared spectral region. It is established that such combined treatment provides a means for substantially increasing the transmittance of GaAs crystals to values characteristic of crystals of high optical quality. On the basis of analysis of the infrared transmittance and reflectance data, Raman spectroscopy data, and atomic-force microscopy data on the surface morphology of the crystals, a physical model is proposed to interpret the effects experimentally observed in the crystals. The model takes into account the interaction of radiation defects with the initial structural defects in the crystals as well as the effect of compensation of defect centers by hydrogen during high-frequency treatment.

Fe-doping of GaN layers of 3 in. in diameter and a thickness of 1 mm in a vertical AIX-HVPE reactor is studied. Ferrocen was used as Fe source. It is shown that a sufficient uniformity of growth conditions, a high purity of undoped GaN layers, and a moderate Fe incorporation of 2×10 18 cm −3 allow for growth of semi-insulating GaN layers with a sufficiently high specific resistivity even at elevated temperature. This makes the material suitable as substrate for electronic power devices at high power or in harsh ambient.

Irradiation of crystalline n-type silicon carbide (n-SiC) with high-energy (53-MeV) argon ions was used to create near-surface semi-insulating (i-SiC) layers. The influence of subsequent heat treatment on the electrical characteristics of i-SiC layers has been studied. The most high-ohmic ion-irradiated i-SiC layers with room-temperature resistivity of no less than 1.6 × 1013 Ω cm were obtained upon the heat treatment at 600°C, whereas the resistivity of such layers heat-treated at 230°C was about 5 × 107 Ω cm.

Comparative study of AuGeNi, Pt, Nd and Gd contacts on semi-insulating (SI) GaAs with respect to the backside quasi-ohmic AuGeNi contact in symmetrical geometry is investigated. Fabricated diode structures are characterized by the current- and capacitance-voltage dependencies. Each of contacts gives an original set of characteristics and current lower that corresponding to the ohmic, bulk limited transport in the initial, low bias (

We report a positron annihilation study using state-of-the-art experimental and theoretical methods in n-type and semi-insulating β - Ga 2 O 3. We utilize the recently discovered unusually strong Doppler broadening signal anisotropy of β - Ga 2 O 3 in orientation-dependent Doppler broadening measurements, complemented by temperature-dependent positron lifetime experiments and first principles calculations of positron-electron annihilation signals. We find that split Ga vacancies dominate the positron trapping in β - Ga 2 O 3 single crystals irrespective of the type of dopant or conductivity, implying concentrations of at least 1 × 1 0 18 c m - 3.

The intrinsic rate capability and the ageing properties of the Resistive Plate Chambers are closely related to the electrodes material and to the front-end electronics threshold. The development of a low noise pre-amplifier led us to improve the intrinsic rate capability of High Pressure Laminate (bakelite) up to $\sim10\;kHz/cm^2$, nevertheless the effective rate is significantly limited by electrodes ageing. To further improve the effective rate capability new materials are investigated. A Resistive Plate Chamber with crystalline semi-insulating Gallium Arsenide electrodes has been characterized with high energy electrons beam at the Beam Test Facility (BFT), (INFN National Laboratory of Frascati, Italy). The response of the Resistive Plate Chamber to multiple bunched electrons was measured operating the detector in avalanche mode. The intrinsic rate capability has been also measured operating the detector in a uniform high energy gamma radiation field at the GIF++ facility (EHN1 of SPS, CERN)., 6 pages, 7 figures

It is shown that 9-μm-thick semi-insulating surface layers can be formed in moderately doped n-type silicon carbide (donor concentration 2 × 1016 cm–3) via the comparatively low-dose (7 × 1011 cm–2) implantation of high-energy (53 MeV) argon ions. The free-carrier removal rate is estimated at ~104 cm–1. The resistivity of the semi-insulator is no less than 7 × 1012 Ω cm. Analysis of the monopolar current of electron injection into the semi-insulator shows that the impurity-conductivity compensation is due to radiationinduced defects pinning the equilibrium Fermi level at a depth of 1.16 eV below the conduction-band bottom. The density of defect states at the Fermi level is 2.7 × 1016 cm2 eV–1.

We studied the hydrogen passivation/depassivation of four types of intrinsic defects (EI5/6, HEI7/8, HEI9/10, and P6/7) in p-type and semi-insulating 4H-SiC by means of electron spin resonance (ESR) for examining the origin of career-lifetime-killing defects. We suggest that the HEI7/8 and P6/7 centers are the strongest candidate for the origin of the lifetime-killing defects.

Because the conditions under which semi-insulating 4H-SiC crystals can grow are so specific, other polytypes such as 15R and 6H can easily emerge during the growth process. In this work, a polytype stabilization technology was developed by altering the following parameters: growth temperature, temperature field distribution, and C/Si ratio. In the growth process of high-purity semi-insulating 4H-SiC crystals, the generation of undesirable polytypes was prevented, and a crystal 100 % 4H-SiC polytype was obtained. A high C/Si ratio in powder source was shown to be advantageous for the stabilization of the 4H polytype. Several methods were applied to evaluate the quality of crystals precisely; these methods include Raman mapping, X-ray diffraction, and resistivity mapping. Results showed that the 3inch-wafer was entirely made of 4H polytype, the mean value of FWHM was approximately 40 arcsec, and the distribution of the resistivity value was between 106 Ω×cm and 107 Ω×cm.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12914

It has been established that hydrogen (H) plays a key role in p-type doping of GaN and it must be removed by dissociation of the Mg–H complex in order to achieve p-type conductivity. However, in carbon (C)-doped semi-insulating GaN, which is the core component of power electronic devices, the role of H, especially the formation and dissociation process of C–H defects, has remained to date a mystery. In this work, we provide a direct evidence for the interaction between H and C in the form of the C N − H i complex in as-grown C-doped GaN. The complex can be dissociated into C N − and H + after post-growth annealing. The activation energy is estimated to be about 2.3–2.5 eV from the temperature-dependent annealing experiments. Our study reveals that the C N − H i complex plays an essential role in understanding the variation of optical and electronic properties of C-doped GaN.

A new terahertz (THz) photomixer based on semi-insulating GaAs (SI-GaAs) with silver nanowire (Ag-NW) is for the first time demonstrated for continuous wave (CW) THz radiation. The use of the Ag-NW greatly enhanced the THz output power (‘” two order of magnitude) and compensated the large carrier lifetime of the SI-GaAs photoconductor.

In this work, we study the breakdown electric field and resistivity of Fe-doped semi-insulating GaN substrates with various Fe doping concentrations. The substrate with Fe doping concentration of 4×1020 cm−3 exhibited an effective lateral breakdown field of 2 MV/cm with a resistivity of more than 1012Ωcm. It was found that increasing the Fe concentration was effective to enhance the resistivity and effective lateral breakdown electric field.

Carbon (C) doping is essential for producing semi-insulating GaN for power electronics. However, to date the nature of C doped GaN, especially the lattice site occupation, is not yet well understood. In this work, we clarify the lattice site of C in GaN using polarized Fourier-transform infrared and Raman spectroscopies, in combination with first-principles calculations. Two local vibrational modes (LVMs) at 766 and $774\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ in C doped GaN are observed. The $766\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ mode is assigned to the nondegenerate ${A}_{1}$ mode vibrating along the $\mathbit{c}$ axis, whereas the $774\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ mode is ascribed to the doubly degenerate $E$ mode confined in the plane perpendicular to the $\mathbit{c}$ axis. The two LVMs are identified to originate from isolated ${\mathrm{C}}_{\mathrm{N}}^{\ensuremath{-}}$ with local ${C}_{3v}$ symmetry. Experimental data and calculations are in outstanding agreement both for the positions and the intensity ratios of the LVMs. We thus provide unambiguous evidence of the substitutional C atoms occupying the N site with a $\ensuremath{-}1$ charge state in GaN and therefore bring essential information to a long-standing controversy.