Gallium Arsenide Samples Research Articles

Active Surface Passivation for mesa type short-wave infrared InGaAs Photodetectors

We propose a gate-controlled device structure for mesa-type infrared photon detectors with the means of improving surface conditions. Additional terminal added to the pn-junction allows surface charges to be manipulated by applying a constant E-field through a metal–oxide–semiconductor (MOS) structure. Short-wave infrared (SWIR) Indium Gallium Arsenide (InGaAs) sample with a cut-off wavelength of 1.69 μm is characterized. A theoretical framework is provided to gating mechanism. Experimental results show that, the shunt component of the dark current improved as high as 63% by interrupting the channel formation on the surface. Further improvements in the generation–recombination (GR) current is noted at more than 90% at 300 K. The effective GR lifetime of 20 μs is obtained under 50 V/μm surface-gate bias.

USE OF POROUS LAYERS OF GALLIUM ARSENIDE AS ATOMIC HYDROGEN SENSORS

The modern development of nanotechnologies, gadgets, and robotics is closely related to the use of nanosized particles of metals, dielectrics, and semiconductors. Composite heterosystems based on semiconductors are used in the creation of advanced opto- and nanoelectronic devices. The operation of such devices is based on the phenomena of excitation of the electronic subsystem of the conductor. The paper investigates the occurrence of non-equilibrium chemiconductivity in gallium arsenide (GaAs) samples when the sample surface is in contact with atomic hydrogen. The effect occurs due to the non-thermal generation of electron-hole (e–h) pairs in the semiconductor wafer, thanks to the energy released during the chemical interaction of hydrogen atoms with the GaAs surface (adsorption and recombination of atoms with the formation of H2 molecules). The kinetics of chemiconductivity was studied, as well as the dependence of chemiconductivity on the density of the flow of atoms per sample and temperature. It was found that the process of generation of (e–h) pairs involves both acts of adsorption of atoms and acts of recombination of atoms into a molecule. The revealed effect of the appearance of non-equilibrium conductivity in samples of single-crystal gallium arsenide during recombination on the surface of atomic hydrogen clearly indicates the presence of effective channels for the accommodation of chemical energy by the conductor when a chemical reaction occurs on its surface. To increase the sensitivity of such a sensor by increasing the area of the "active" surface, it is proposed to use a porous layer of GaAs (por-GaAs). The phenomenon of non-equilibrium chemiconductivity in porous gallium arsenide, discovered and investigated for the first time in this paper, opens up wide prospects for the use of this semiconductor for the direct conversion of chemical energy into electrical energy. Semiconductors with a narrow bandgap of this type have prospects in the development of devices for the direct conversion of chemical energy into electrical energy, as well as in the creation of chemical sensors. The possibility of using this material as a detector of hydrogen atoms in the gas phase is substantiated.

Optical and Surface Structure Modification of Gallium Arsenide

The surface morphology modification and optical property modification of semi-insulating gallium arsenide sample implanted with 100 keV silicon ions with the fluences ranging between 5 × 10[Formula: see text] and 4 × 10[Formula: see text] ion cm[Formula: see text] were analyzed using scanning electron microscopy and UV–Vis–NIR spectroscopy study. Scanning electron microscopy study revealed pore-like structure formation on the surface of gallium arsenide samples after silicon ion implantation. The size of these pore-like structures was found to increase with increasing ion fluence. Energy dispersive X-ray analysis showed an increase in silicon concentration in the gallium arsenide sample after silicon ion implantation with increasing ion fluence. The UV–Vis–NIR spectroscopy study revealed a decrease in optical transmission for silicon ion implanted gallium arsenide sample with increasing ion fluence. An additional absorption band was observed for the gallium arsenide sample implanted with the highest fluence (4 × 10[Formula: see text] ion cm[Formula: see text]. Urbach tail energy was found to increase with respect to ion fluence.

Application of Proton Irradiation in the Study of Accelerated Radiation Ageing in a GaAs Semiconductor.

Proton irradiation experiments have been used as a surrogate for studying radiation effects in numerous materials for decades. The abundance and accessibility of proton accelerators make this approach convenient for conducting accelerated radiation ageing studies. However, developing new materials with improved radiation stability requires numerous model materials, test samples, and very effective utilization of the accelerator beam time. Therefore, the question of optimal beam current, or particle flux, is critical and needs to be adequately understood. In this work, we used 5 MeV protons to introduce displacement damage in gallium arsenide samples using a wide range of flux values. Positron annihilation lifetime spectroscopy was used to quantitatively assess the concentration of radiation-induced survived vacancies. The results show that proton fluxes in range between 1011 and 1012 cm-2.s-1 lead to a similar concentration of monovacancies generated in the GaAs semiconductor material, while a further increase in the flux leads to a sharp drop in this concentration.

Simulating the process of steady-state thermoreflectance for measuring the thermal conductivity of materials

The measurement of thermal conductivity by the method of steady-state thermoreflectance is based on the effect of heating the sample by laser radiation. The power of reflected radiation from the sample is measured using an additional probe laser. The change in the reflection coefficient of the studied material due to the heating is proportional to the change of the sample temperature. The radiation power absorbed by the material acts as a volumetric heat source. The value of thermal conductivity is calculated according to the Fourier’s law of thermal conductivity. A steady-state thermoreflectance setup requires calibration, i.e., thermal conductivity measurement of reference samples. The value of the calibration coefficient, in turn, depends on the characteristics of the lasers used in the setup. In this work, a numerical model of sample heating is proposed which allows considering the shape and diameter of the incident radiation beam, the distribution of radiation power over the beam area, and the absorption and reflection coefficients of the material. A methodology for samples reflection and absorption coefficients determination, including measurements and calculations considering the Fabry-Perot effect, is proposed. The study was performed for the samples of germanium, silicon, gallium arsenide, and sitall. The irradiation was performed with a continuous wave single-mode diode laser with a wavelength of 980 nm. The incident radiation power distribution over the beam area was approximated according to the Gaussian function in the OriginPro software. The radiation power that passed through the samples and reflected from them was measured. The temperature of the samples during irradiation was measured with a thermal imager. The reflection and absorption coefficients of the samples were determined from the results of radiation power measurements using a mathematical model of the interaction of plane-polarized TE electromagnetic radiation with the material. Comparison of the calculation results with the literature data for germanium, silicon, and sitall samples showed their correspondence. For gallium arsenide there was a discrepancy between the calculation results and the literature data. For gallium arsenide samples, a model considering the Fabry-Perot effect was used, and the optical properties were determined numerically by searching for the minimum modules of the transfer functions of the transmitted and reflected radiation in the Matlab program. The model of electromagnetic heating of the investigated samples was implemented in the COMSOL Multiphysics software. A method for the determination of the reflection and absorption coefficients of materials investigated by the steady-state thermorflectance is proposed. The proposed model allows considering beam shape, width and distribution of the radiation power as well as the value of the absorbed radiation power for each sample. The difference between the calculated values of the sample temperature and the measurement results does not exceed 9 %. The model can be applied to measure the thermal conductivity of bulk and thin-film materials with unknown properties.

Pseudo-dielectric function spectra of the near surface layer of GaAs implanted with various fluence of Xe+ ions

Monocrystalline (100) semi-insulating gallium arsenide (GaAs) samples were irradiated with a 250-keV Xe+ ion beam at room temperature. To investigate the effect of ion irradiation on GaAs samples, the ion fluence was varied from 1 × 1012 to 3 × 1016 ions/cm2. The spectroscopic ellipsometry (SE) method and the Rutherford backscattering spectrometry (RBS) with nuclear reaction (NR) method were used to determine the properties of the virgin and implanted samples. The SE approach reveals that the pseudo-dielectric function of implanted GaAs samples varies with ion fluence. The RBS approach, which exposes the depth-profile of As, Ga, and Xe in the implanted samples, allows us to correlate changes in the pseudo-dielectric function with structural modifications caused by the ion irradiation. The NR approach points out the existence of an oxygen-enriched layer on the surface of implanted GaAs samples. Lastly, the optical study involving the Cauchy and Urbach dispersion model measures the refractive index n and extinction coefficient k of the native oxide layer on the surface of GaAs samples.

Quantification of Aluminum Gallium Arsenide (AlGaAs) Wafer Plasma Using Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS).

In this work, we report the results of the compositional analysis of an aluminum gallium arsenide (AlGaAs) sample using the calibration-free laser-induced breakdown spectroscopy (CF-LIBS) technique. The AlGaAs sample was doped with three various concentrations of gallium (Ga), arsenic (As), and aluminum (Al), as reported by the manufacturer, and the CF-LIBS technique was employed to identify the doping concentration. A pulsed Q-switched Nd: YAG laser capable of delivering 200 and 400 mJ energy at 532 and 1064 nm, respectively, was focused on the target sample for ablation, and the resulting emission spectra were captured using a LIBS 2000+ spectrometer covering the spectral range from 200 to 720 nm. The emission spectra of the AlGaAs sample yielded spectral lines of Ga, As, and Al. These lines were further used to calculate the plasma parameters, including electron temperature and electron number density. The Boltzmann plot method was used to calculate the electron temperature, and the average electron temperature was found to be 5744 ± 500 K. Furthermore, the electron number density was calculated from the Stark-broadened line profile method, and the average number density was calculated to be 6.5 × 1017 cm−3. It is further observed that the plasma parameters including electron temperature and electron number density have an increasing trend with laser irradiance and a decreasing trend along the plume length up to 2 mm. Finally, the elemental concentrations in terms of weight percentage using the CF-LIBS method were calculated to be Ga: 94%, Al: 4.77% and As: 1.23% for sample-1; Ga: 95.63%, Al: 1.15% and As: 3.22% for sample-2; and Ga: 97.32%, Al: 0.69% and As: 1.99% for sample-3. The certified concentrations were Ga: 95%, Al: 3% and As: 2% for sample-1; Ga: 96.05%, Al: 1% and As: 2.95% for sample-2; and Ga: 97.32%, Al: 0.69% and As: 1.99% for sample-3. The concentrations measured by CF-LIBS showed good agreement with the certified values reported by the manufacturer. These findings suggest that the CF-LIBS technique opens up an avenue for the industrial application of LIBS, where quantitative/qualitative analysis of the material is highly desirable.

Raman and RBS Analysis of Silicon Ion Implanted Gallium Arsenide

This paper analyzes the effect of 100[Formula: see text]keV silicon negative ion implantation in semi-insulating gallium arsenide sample for the fluences varying between [Formula: see text] and [Formula: see text][Formula: see text]ion[Formula: see text]cm[Formula: see text] using Raman spectroscopy, Rutherford backscattering spectroscopy and Electron spin resonance spectroscopy. The gallium arsenide sample implanted with silicon negative ion for different fluences showed shift in the TO peak position with respect to unimplanted gallium arsenide sample. Increase in the broadening of TO peak was observed in the as-implanted samples, indicating development of stress and phonon confinement due to the incorporation of silicon in gallium arsenide crystal lattice. Annealing of as-implanted samples showed stress relaxation. Increase in RBS backscattering yield was observed in the as-implanted samples. Annealing of as-implanted (with high fluence) sample showed flat RBS yield response. ESR measurement study revealed restructuring of defects in the gallium arsenide sample implanted with fluence of [Formula: see text][Formula: see text]ion[Formula: see text]cm[Formula: see text] after annealing to the temperature of [Formula: see text]C.

Comparison of the results of optical and electrophysical measurements of free electron density in n-GaAs samples doped with tellurium

A theoretical model has been developed that allows one to determine free electron density in n-GaAs from the characteristic points on far-infrared reflection spectra. It was shown that, in this case, it is necessary to take into account the plasmon-phonon coupling (otherwise, the electron density is overestimated). The calculated dependence of electron density, Nopt, on the characteristic wave number, ν+, which is described by a second degree polynomial, has been obtained.Twenty-five tellurium-doped gallium arsenide samples were used to measure the electron density in two ways: according to traditional four-contact Hall method (Van der Pauw method) and using the optical method we developed (measurements were carried out at room temperature). Based on the experimental results, the dependence was constructed of the electron density values obtained from the Hall data, NHall, on the electron density obtained by the optical method, Nopt. It is shown that this dependence is described by linear function. It is established that the data of optical and electrophysical measurements coincide if the electron density is Neq = 1.07 ⋅ 1018 cm-3, for lower values of the Hall density NHall < Nopt, and for large values NHall > Nopt. A qualitative model is proposed to explain the results. It has been suggested that tellurium atoms bind to vacancies of arsenic into complexes, as a result of which the electron density decreases. On the surface of the crystal, the concentration of arsenic vacancies is lower and, therefore, the condition Nopt > NHall should be satisfied. As the doping level increases, more and more tellurium atoms remain electrically active, so electron density in the volume begins to prevail over the surface one. However, with a further increase in the doping level, the ratio NHall/Nopt again decreases, tending to unity. This, probably, is due to the fact that the rate of decomposition of the complexes “tellurium atom + arsenic vacancy” decreases with increasing doping level.

Carrier Scattering Mechanisms: Identification via the Scaling Properties of the Boltzmann Transport Equation

AbstractA method based on the scaling properties of the Boltzmann transport equation is proposed to identify the dominant scattering mechanisms that affect charge transport in a semiconductor. This method uses drift velocity data of mobile charges at different lattice temperatures and applied electric fields and takes into account the effect of carrier heating. By performing time‐of‐flight measurements on single‐crystalline diamond, hole and electron drift velocities are measured under low‐injection conditions within the temperature range 10–300 K. Evaluation of the data using the proposed method identifies acoustic phonon scattering as the dominant scattering mechanism across the measured temperature range. The exception is electrons at 100–200 K where conduction‐band valley repopulation has a prominent effect. At temperatures below ≈80 K, where valley polarization is observed for electrons, transport dominated by acoustic phonon scattering is observed in different valleys separately. The scaling model is additionally tested on data from highly resistive gallium arsenide samples to demonstrate the versatility of the method. In this case, impurity scattering can be ruled out as the dominant scattering mechanism in the samples for the temperature range 80–120 K.

Raman LO phonon signal and two dimensional AFM studies on GaAs implanted by Mn ions and impact of irradiation with 5 MeV Si++ ions on it

In the present work, gallium arsenide samples implanted with 325 keV Mn+ ions for the fluence of 5 × 1015, 1 × 1016 and 2 × 1016 ions cm−2, have been investigated using Raman scattering and Atomic force microscopy measurements. The sample implanted with the fluence of 1 × 1016 ions cm−2 was further irradiated using 5 MeV Si++ ion beams for the fluence of 1 × 1016 ions cm−2 at a substrate temperature of 350°C for recrystallization. Raman peaks obtained at 293.51 and 269.35 cm−1 were assigned to longitudinal optical (LO) phonon mode and transverse optical (TO) phonon mode of gallium arsenide, respectively. The shift in the Raman peaks towards higher wave-number with respect to ion fluence indicated the presence of residual compressive stress within the samples. The Mn and (MnAs) like mode were observed after implantation. The additional mode like GaMn was also seen in sample after irradiation with 5 MeV Si++ ions. The composition of manganese atoms in gallium arsenide estimated from the Raman spectra for the ion fluence 5 × 1015, 1 × 1016 and 2 × 1016 ions cm−2 were found to be 0.74%, 1.40% and 2.80%, respectively. The Phonon coherence length estimated from the Phonon Confinement Model by fitting the LO phonon signal was found to increase from 39.40 to 47.10 nm with respect to ion fluence. AFM images of non-implanted sample showed the smooth micrograph with root mean square surface roughness of 0.41 nm. After implantation, the different sizes of clusters were observed on the surfaces of GaAs. The shape and size of the clusters were found to depend on the ion fluence.

GaAs as a Bright Cryogenic Scintillator for the Detection of Low-Energy Electron Recoils From MeV/c2 Dark Matter

This article presents the measurements of the luminescence and scintillation under X-ray of undoped, Si-doped, and Si, B codoped gallium-arsenide (GaAs) samples at cryogenic temperature over a wide infrared (IR) region using Si and InGaAs photodetectors. The undoped GaAs has a narrow emission band at 838 nm (1.48 eV) and a low light output of about 2 ph/keV. The GaAs:Si has three broad luminescence bands at 830 nm (1.49 eV), 1070 nm (1.16 eV), and 1335 nm (0.93 eV) and a light output of about 67 ph/keV. GaAs:(Si, B) has four luminescence bands at 860 nm (1.44 eV), 930 nm (1.33 eV), 1070 nm (1.16 eV), and 1335 nm (0.93 eV) with a light yield of approximately 119 ph/keV. With advances in photodetection, GaAs promises to be a useful cryogenic scintillator for the detection of electron recoils from MeV/c2 dark matter.

Effects of silicon negative ion implantation in semi-insulating gallium arsenide

ABSTRACTIn 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 keV have been described. Atomic force microscopic images obtained from samples implanted with fluence up to 1 × 1017 ion cm−2 showed the formation of GaAs clusters on the surface of the sample. The shape, size and density of these clusters were found to depend on ion fluence. Whereas sample implanted at higher fluence of 4 × 1017 ions cm−2 showed bump of arbitrary shapes due to cumulative effect of multiple silicon ion impact with GaAs on the same place. GXRD study revealed formation of silicon crystallites in the gallium arsenide sample after implantation. The silicon crystallite size estimated from the full width at half maxima of silicon (111) XRD peak using Debye-Scherrer formula was found to vary between 1.72 and 1.87 nm with respect to ion fluence. Hall measurement revealed the formation of n-type layer in gallium arsenide samples. The current–voltage measurement of the sample implanted with different fluences exhibited the diode like behavior.

Features of Stationary Photoconductivity of High-Ohmic Semiconductors Under Local Illumination

Photoconductivity has been thoroughly studied for a long time. However, most researchers have examined photoconductivity of semiconductors while illuminating the entire surface of samples. The present paper examines the effect of local exposure that ensures a high level of injection of free charge carriers upon the conductivity of high-ohmic cadmium telluride and semi-insulating gallium arsenide samples and upon the properties of ohmic contacts to samples. The authors found that regardless of the exposure area the value of transition resistance of ohmic contacts decreases and the concentration of the main charge carriers increases in the sample in proportion to radiation intensity. This research uncovered a number of previously unknown effects that are interesting from the physical point of view. This paper focuses on discussing these effects.

High Resolution Parameter-Space from a Two-Level Model on Semi-Insulating GaAs

Semi-insulating Gallium Arsenide ( SI-GaAs ) samples experimentally show, under high electric fields and even at room temperature, negative differential conductivity in N-shaped form (NNDC). Since the most consolidated model for n-GaAs , namely, "the model", proposed by E. Schöll was not capable to generate the NNDC curve for SI-GaAs , in this work we have proposed an alternative model. The model proposed, "the two-valley model" is based on the minimal set of generation-recombination equations for two valleys inside of the conduction band, and an equation for the drift velocity as a function of the applied electric field, that covers the physical properties of the nonlinear electrical conduction of the SI-GaAs system. The "two-valley model" was capable to generate theoretically the NNDC region for the first time, and with that, we were able to build a high resolution parameter-space of the periodicity (PSP) using a Periodicity-Detection (PD) routine. In the parameter-space were observed self-organized periodic structures immersed in chaotic regions. The complex regions are presented in a "shrimp" shape rotated around a focal point, which forms in large-scale a "snail shell" shape, with intricate connections between different "shrimps". The knowledge of detailed information on parameter spaces is crucial to localize wide regions of smooth and continuous chaos.

Photo -Dielectric Investigation of p- Gallium Arsenide

The complex dielectric constant of gallium arsenide sample was studied in the frequency range 0.3 to 30 MHz, subjected to photo-excitation. The model proposed by Dutt and Nicholls for after glow plasma seems to be in agreement with the experimental results. The relaxation time and damping have been estimated.

Modification of the Van der Pau method for measuring electrophysical parameters of high-resistance semiconductors

It is shown that the Van der Pau method can be used under illumination of the sample near-contact region with monochromatic radiation of variable intensity with a quantum energy that exceeds the investigated-material band gap. A modified Van der Pau technique for measuring such high-resistance semiconductor parameters as the electrical resistivity and the free-carrier concentration and mobility is proposed. This technique was tested on a semi-insulating n-type gallium arsenide sample with a free-electron concentration at room temperature of ∼107 cm−3.

Use of contact illumination for high-resistance semiconductor conductivity measurements

It is shown that illumination of ohmic contacts to high-resistance cadmium telluride and gallium arsenide samples affects not only the transient resistance of the contact, but the bulk conductivity of samples by increasing the concentration of free charge carriers. The model explaining the increase in the volume conductivity of the sample under the illumination of the contact region is presented. The procedure for separate determination of the transient resistances of the ohmic contact and the sample volume, suitable for highresistance semiconductors, is proposed.

A novel method to measure dielectric properties of materials in terahertz spectroscopy

We present a simple method to obtain the optical and dielectric properties of samples without reference measurement in the reflection-type terahertz time-domain spectroscopy. The dielectric properties of the samples of silicon and gallium arsenide were examined. The optical and dielectric properties of the samples were measured through only simple configuration, without the misplacement error. The obtained dielectric functions of the samples in reflection geometry are in good agreement with that predicated by the theory. The main advantage of this method over other methods is its simplicity and accuracy and ease for application of the reflection systems with different incident angle.

Determination of the Peltier coefficient for gallium arsenide in a vertical Bridgman furnace

The Peltier coefficient for gallium arsenide solid in contact with its melt was experimentally determined. Selenium doped gallium arsenide samples were hermetically sealed in a fused quartz ampoule and processed in a vertical Bridgman furnace. During the translation period seven sequences of current-on and current-off periods were processed into the solidifying crystal. An axial slice was mechanochemically polished and then etched. Photomicrographs of the slice were taken with differential interference contrast microscopy and were used to measure the thickness of the current-on and current-off layers. These results were used to calculate growth rates from which the Peltier coefficient was calculated. An average value of 0.107±0.015 V was determined. The values calculated from the different sequences were in excellent agreement with each other even though the sequences had different current densities, current-on durations, and current-on to current-off ratios.