Tellurium-doped Gallium Arsenide Research Articles

Effect of a Travelling Magnetic Field on the Parameters of Tellurium-Doped Gallium Arsenide Single Crystals Grown by the Czochralski Method

Effect of a Travelling Magnetic Field on the Parameters of Tellurium-Doped Gallium Arsenide Single Crystals Grown by the Czochralski Method

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.

Investigation of the process of reactive ion-beam sputtering of gallium arsenide using optical emission spectroscopy

The aim of this work was to study the process of reactive ion-beam sputtering of gallium arsenide using optical emission analysis of plasma in the target region to determine the optimal conditions for the formation of intrinsic GaAs oxides. The ion source was a plasmatron based on an anode layer accelerator (UAS), which generated a stream of accelerated argon and oxygen ions with an energy of 400–1200 eV. The target was made from tellurium doped gallium arsenide. Intense GaI lines (2874.2 Å, 2943.6 Å, 4033.0 Å and 4172.1 Å), atomic argon ArI, argon ions, and also FeI lines were detected in the spectrum upon sputtering of GaAs by Ar+ ions. The appearance of iron lines can be explained by the sputtering of the pole tips of the magnetic system of the ion source. An increase in the accelerating voltage from 1 to 3 kV leads to an increase in the intensity of the peaks of atomic gallium GaI (4172.1 Å) by 2.38 times, the GaI line (4033.0 Å) by 3.25 times, the GaI line (2943.6 Å) 3.4 times, GaI lines (2874.2 Å) 5 times. It was found that an increase in the partial pressure of oxygen leads to a sharp decrease in the peaks of GaI (4033.0 Å) and GaI (4172.1 Å) due to the chemical interaction of gallium and oxygen. Sputtering in pure oxygen reduces the intensity of these peaks by 8 and 5 times, respectively. The intensities of the peaks of atomic gallium GaI (2874.2 Å) and GaI (2943.6 Å) decreased in 2 and 1.78 times, respectively. In the presence of a positive potential on the target, the intensity of all lines of atomic gallium monotonically decreases with increasing potential. In the emission spectrum, lines of atomic oxygen OI (7774.2 Å) and molecular positive ions O+2 (6418.7 Å, 6026.4 Å, 5631.9 Å and 5295.7 Å) were detected. In the presence of a positive potential on the target, a monotonic decrease in the intensity of the above oxygen lines was observed. This indicates an intensification of chemical interaction of oxygen with target elements and, accordingly, a decrease in the free active oxygen particles.

Structural Features Associated with Twinning in the Growth of Gallium Arsenide Single Crystals by the Czochralski Method

The structural features induced by twinning in tin- and tellurium-doped gallium arsenide crystals during their growth by the Czochralski method with liquid melt sealing by boric anhydride have been considered. It is shown that growth twins and edge facets arise at the crystal periphery in the region of supercooled melt. The dopant concentration near a twin is always higher than in the region free of twins. A change is observed in the dislocation-growth direction in crystal during twinning.

Investigation of Alloyed Ohmic Contacts in Epitaxial Tellurium-Doped Gallium Arsenide Layers

The conditions for the growth of epitaxial layers are considered and the resistance of alloyed ohmic contacts to tellurium-doped gallium arsenide layers is studied. The use of the (AuGe eutectic alloy)-Ni–Au composition alloy of ohmic contacts to the gallium arsenide layers with electron conductivity, including use as a contact layer of a narrow-band (In0.5Ga0.5As), makes it possible to achieve a resistance of 10–7 Ohm cm2, in the best case; however, this leads to a deterioration of the surface morphology. In this paper, we study the issues of doping the GaAs contact layer by tellurium to the maximum concentration of 2.5 × 1019 cm–3. In this case, the resistance of the ohmic contacts proves to be less than 5 × 10–8 Оhm cm2, simultaneously with the improvement of the semiconductor’s surface morphology.

Electrical properties of tellurium-doped gallium arsenide thin films

Electrical properties of tellurium-doped gallium arsenide thin films

Complexing of tellurium-doped gallium arsenide in gas-phase epitaxy

The effect of the conditions of gas-phase epitaxy on complexing in tellurium-doped layers of gallium arsenide is studied. Measurements of the intensities of the corresponding photoluminescence lines were used to estimate the concentration of optically-active complexes. A correlation was found between the processes involved in complexing, the growth velocity, and impurity trapping in the layers. The determining role of the surface structure in the formation of complexes, including impurity atoms, is demonstrated.

A defect model for undoped and tellurium doped gallium arsenide

A defect model for undoped and tellurium doped gallium arsenide

A defect model for undoped and tellurium doped gallium arsenide

The introduction of two new defects, both 〈100〉 split-interstitials, can explain the experimental results obtained from annealing studies on undoped and tellurium doped gallium arsenide. This model concludes that the arsenic and gallium Frenkel reactions only occur at annealing temperatures above 4̃00 and 9̃00°C respectively and suggests that gallium diffuses by occupying split-interstitial sites. This model also suggests that interestitial arsenic may occupy the hexagonal interstitial sites.

Preferential precipitation on dislocation loops in Te-doped gallium arsenide

Abstract Heat-treated tellurium-doped gallium arsenide contains prismatic and faulted dislocation loops with precipitate particles lying on the dislocation core. The position of the precipitates on the loops has been studied revealing preferential precipitation on 〈110〉 line segments for both faulted and prismatic loops. From a consideration of the atomic arrangements at the dislocation cores it is concluded that the precipitates preferentially decorate the prismatic loops where the dislocation core is identical to either a βss or αgs Lomer dislocation. Precipitates on the {111} faulted loops, however, can appear on all possible 〈110〉 dislocation segments. The faulted loops are thought to consist of a layer of gallium telluride, and, since this is a defect lattice containing gallium vacancies, β type dislocation core structures can occur along all six 〈110〉 directions. By analogy with the faulted loops, preferential precipitation on prismatic loops is believed to occur on βss Lomer dislocations.

Interstitial condensation in n+ GaAs

Transmission electron microscopy of annealed tellurium-doped gallium arsenide has shown that a high constitutional interstitial defect population is present in n+ as-grown material. The point defects precipitate into the form of perfect interstitial dislocation loops when annealed above 380°C. The equivalent point defect concentration within the loops remains constant during isochronal and isothermal anneals and is dependent on the tellurium level. Copper diffusion is also found to influence the point defect concentration and copper may be the element responsible for the formation of the precipitates often associated with the large dislocation loops.

The nature of inclusions in heavily tellurium-doped gallium arsenide

Large elongated inclusions in heavily Te-doped 〈001〉 Czochralski pulled, GaAs crystals have been studied by a combination of scanning and transmission electron microscopy, electron microprobe analysis and X-ray topography. They have been shown to lie along the 〈110〉 directions in the {001} growth plane and to consist of two parts, an outer single crystal region of varying composition based on Ga2Te3 and an inner polycrystalline core rich in Te and As. Their crystallography has been interpreted in terms of impurity segregation and facet formation during crystal growth while their composition is discussed with reference to the Ga-As-Te phase diagram.

Electron irradiation of heavily doped GaAs:Si and GaAs:Te

Abstract Infrared optical reflectivity measurement techniques are applied to determine the carrier removal rate, mobility changes, and annealing characteristics of heavily doped n-type silicon or tellurium-doped gallium arsenide. 1 MeV room temperature electron irradiation reduces both the carrier concentration and the mobility. Removal rates for GaAs: Te and GaAs:Si having initial carrier concentrations of 6 × 1018 cm−3 are approximately 3.4 and 3.0 cm−1 respectively. The mobility degrades exponentially as a function of fluence. Isochronal anneal experiments show one major recovery stage between 170 and 230°C, and the results are in reasonable agreement with previous data obtained by electric measurements on more lightly doped n-type GaAs.

Electrical and electron microscope studies of the annealing of tellurium-doped gallium arsenide

Abstract Hall effect measurements and electron microscope examination of tellurium-doped gallium arsenide crystals annealed at various temperatures indicate that tellurium and copper (present as a contaminant) produce a high population of matrix point defects which are probably simple vacancies. Annealing at temperatures below 1000°C causes the growth of intrinsic prismatic vacancy loops on {111} and {100} planes in association with decorations of precipitated copper. Heating to temperatures above 1000°C caused the copper and tellurium (in extrinsic stacking faults) to move back into solution, eventually changing the semiconductor from n to p type, and leading to the disappearance of both prismatic loops and stacking faults.

Parameters of injection lasers made of gallium arsenide crystals with different dislocation densities

An investigation was made of the influence of growth dislocations on the watt-ampere (output radiation-injection current) characteristics of injection lasers made of tellurium-doped gallium arsenide, in which the carrier density was (1–3) · 1018 cm−3. These lasers were prepared from plates where the dislocation density ranged from 102 to 105 cm−2. It was established that the optical inhomogeneity of the plates was not related to the distribution of the dislocations in the bulk of the material. No definite correlation was found between the dislocation density in the original crystals and the laser parameters such as the pulse output power, efficiency, or threshold current density.

Image contrast of triple loops in tellurium-doped gallium arsenide

Abstract The contrast of the bounding partial dislocations of three-layer loops in tellurium-doped gallium arsenide has been examined in the electron microscope and compared with the calculated dislocation profiles for different diffracting conditions. The triple loops are shown to consist of three overlapping extrinsic stacking faults, each fault bounded by a Frank partial dislocation with Burgers vector b=+1/3 [lll].