Hall effect and conductivity measurements over a wide temperature range of 20-300 K are carried out on gallium-doped silicon subjected to 3.5 MeV electron and 15 MeV proton irradiation at room temperature. Electrical data obtained provide convincing evidence that impurity atoms are involved in interactions with intrinsic point defects during irradiation. As a result, heavy losses of the shallow acceptors in the irradiated samples are found. Then, to shed light on the electrical properties of the radiation-produced defects, these samples are subjected to annealing. Two kinds of defects, Ga-vacancy pairs and substitutional Ga--interstitial Ga+ ion pairs, are earlier discussed in the literature. However, a new kind of Ga-related radiation defects that are electrically neutral in p-type materials makes its appearance as well. In fact, under our irradiation conditions, they turn out to be dominant and stable up to 450 degrees C. Interstitial Ga-related defects in the irradiated samples are believed to be responsible for the anisotropic effects observed for the hole mobility at cryogenic temperatures. Similar anisotropic effects are also observed in boron-doped silicon subjected to electron and proton irradiation. Some interesting peculiarities in the formation processes of interstitial Ga-related defects are discussed.

Electrical properties of defects produced in strongly bismuth-doped silicon by 15 MeV protons are investigated in detail. Electrical measurements on irradiated samples by means of the van der Pauw technique are conducted over a wide temperature range of 20–300 K to furnish information on radiation-produced complexes. It is shown that the properties of the dominant bismuth-related defects are the same as earlier found in the electron-irradiated material. These complexes are tentatively identified as bismuth–vacancy pairs being deep donors. Their atomic configuration appears to be radically different from what is known about similar vacancy-related defects with other group-V impurities. These bismuth-related pairs are stable up to T ≈ 300 °C. Some special features of defect formation and annealing processes of radiation defects in bismuth-doped silicon subjected to electron and proton irradiation are discussed. This information may be of advantage in modeling impurity-related complexes containing oversized impurity atoms in silicon.

Mechanical stress in the surface layers of silicon wafers subjected to a bending mode of central symmetry is investigated by Raman spectroscopy. An original setup for bending wafers makes it possible to simultaneously take optical measurements on the stretched and compressed sides of silicon wafers. On the stretched and compressed sides of the silicon wafers used in this work, the mechanical stress produces an elastic deformation of 0.42% and 0.18%, respectively.

The zone fluctuation potentials (ZFPs) in quantum wells located in the space charge region (SCR) of the p–n junction and the lateral ZFPs in quantum wells outside the SCR in blue, green, and UV LEDs based on nitrides have been experimentally determined. Green LEDs were used as an example to show that the low external quantum efficiency (EQE) of LEDs at the maximum correlated with an increase in the ZFP and disordering of heteroboundaries in quantum wells located in the SCR. The EQE at the maximum decreased because charge carriers were captured by charged centers localized at disordered heteroboundaries. The lateral ZFP in quantum wells located outside the SCR was the main parameter determining the decrease of the EQE from the moment the p–n junction opened until current densities reached 30–40 A/cm2.

Electrical measurements are taken on bismuth-doped silicon subjected to electron irradiation at room temperature. The analysis of experimental data obtained in a temperature interval of 30–300 K shows a considerable decrease in the concentration of the shallow donor states of Bi in irradiated samples due to the formation of electrically neutral Bi-related complexes, which, in turn, are ascribed to bismuth–vacancy pairs. They are very stable up to T ≈ 300 °C. The contribution of radiation-produced acceptors in an irradiated material appears to be of minor importance. Unexpectedly, the behavior of the mobility of charge carriers in the course of irradiation and isochronal annealing displays very strange features. It is thought that this striking effect is accounted for by a split atomic configuration of bismuth–vacancy pairs, in sharp contrast to the well-known configuration of phosphorus–vacancy and arsenic–vacancy pairs.

The contribution of several mechanisms into the external quantum efficiency (EQE) droop in green InGaN/GaN LEDs over a temperature increase from 300 to 400 K is clarified. One of them is the ionization of atoms localized at disordered hetero-interfaces in InGaN/GaN MQWs situated at the depletion region around a p-n junction at j < 10 A/cm2 and U < Utr (turn on voltage). The ionized atoms capture tunneling charge carriers, which leads to EQE decrease. Another mechanism is the capture of charge carriers tunneling in 3D spaces of MQWs situated outside of a depletion region at U > Utr and 10 A/cm2 < j < 30 A/cm2. Grow-ing thermalized carriers concentration reduces the band fluctuation potential which results in vertical diffusion transport of carriers and crowding effect.

In this paper formation and annealing of boron-related defects in p-type silicon grown by the floating zone technique and subjected to electron and proton irradiation at room temperature are discussed. The defect model suggested earlier has provided fresh insight into the nature of two dominant complexes containing boron in irradiated p-Si, among them boron-divacancy complexes and interstitial boron-substitutional boron pairs. In the present work the same material is irradiated with 6 MeV electron and 8 MeV protons providing additional electrical data to test this model. Additionally new information on boron-related defects in heavily doped p-Si subjected to irradiation with 2.5 MeV electrons at 4.2 K and then subjected to isochronal anneals above room temperature is also discussed. The results obtained on proton irradiated p-Si(FZ) testify that the annealing behavior of boron-divacancy complexes appears to be complicated, in contrast to the behavior of substitutional boron-interstitial boron pairs. The defect model based on the experimental information furnished so far may be used for testing and refining computerized simulations of Non-Ionizing Energy Loss (NIEL) in irradiated silicon. Keywords: silicon, boron impurity, electron- and proton-irradiation, impurity-related complexes.

A detailed study of boron-related defects in strongly doped p-type silicon subjected to irradiation with 3.5 MeV electrons and 15 MeV protons are carried out by means of electrical measurements over a wide temperature range of 25 ≤ T ≤ 300 K. Investigations are aimed at taking a close look into the nature of radiation-produced defects that are stable at room temperature. Data obtained allow one to reveal two types of dominant boron-related complexes, which are attributed to the substitutional boron-interstitial boron pair being neutral in p-type Si and the substitutional boron-divacancy complex displaying donor activity. The first type of the defects is very stable and its annealing runs in a temperature region of 500–700 °C. Another type of defect turned out to be stable up to 300 °C. The formation and annealing processes of the boron-related defects appear to be very similar for electron and proton irradiation of p-type Si.

Annealing processes of vacancy-impurity atom pairs in moderately doped n-type silicon grown by the floating-zone technique and subjected to 0.9 MeV electron irradiation are investigated by means of Hall effect and conductivity measurements taking over a wide temperature range of 20 to 300 K. Changes in the total concentrations of shallow donors and compensating acceptors in samples prior to and after irradiation as well in the course of isochronal annealing in a temperature interval of 100 to 700°C are determined. It is demonstrated that the Fermi level at annealing stages between 100 and 260°C plays an important part in recovery of the electrical properties of irradiated samples. There is evidence that the first annealing stage between 100 and 160°C is associated with limited migration of vacancy-impurity atom pairs and their trapping by free phosphorus impurity atoms. As a consequence, complexes of vacancy-two impurity atoms appear. They are stable up to 600°C. The complete restoration of the electrical parameters of irradiated samples is observed at 700°C.

A comparative study of interactions of shallow impurities with primary defects in oxygen- and carbon-lean moderately doped Si and Ge subjected to irradiation with 0.9 MeV electrons, 60Co gamma-rays, and 15 MeV protons at room temperature is presented and discussed. For the quantitative characterization of such interactions, changes in the total concentration of the original shallow group-V donor or group-III acceptor impurities in the irradiated materials are determined by Hall effect measurements over a wide temperature range. Losses of the shallow donor or acceptor states in the irradiated Si and Ge are indicative of their removal rates that can be used for estimation of production rates of primary defects interacting with the dopants. Some important factors affecting the interactions between primary defects and shallow impurities in Si and Ge are highlighted.

AbstractA fractal-percolation system that includes extended defects and random fluctuations in the alloy composition is formed during the growth of device structures based on Group-III nitrides. It is established that the specific features of this system are determined not only by the growth conditions. It is shown that the diversity of the electrical and optical properties of InGaN/GaN LEDs (light-emitting diodes) emitting at wavelengths of 450–460 and 519–530 nm, as well as that of the electrical properties of AlGaN/GaN HEMT (high-electron-mobility transistor) structures, is due to modification of the properties of the fractal-percolation system both during the growth process and under the action of the injection current and irradiation. The influence exerted by these specific features on the service life of light-emitting devices and on the reliability of AlGaN/GaN HEMT structures is discussed.

A fractal-percolation system that includes extended defects and random fluctuations in the alloy composition is formed during the growth of device structures based on Group-III nitrides. It is established that the specific features of this system are determined not only by the growth conditions. It is shown that the diversity of the electrical and optical properties of InGaN/GaN LEDs (light-emitting diodes) emitting at wavelengths of 450–460 and 519–530 nm, as well as that of the electrical properties of AlGaN/GaN HEMT (high-electron-mobility transistor) structures, is due to modification of the properties of the fractal-percolation system both during the growth process and under the action of the injection current and irradiation. The influence exerted by these specific features on the service life of light-emitting devices and on the reliability of AlGaN/GaN HEMT structures is discussed.

AbstractRadiation stability of the nanoporous silicon under gamma irradiation was investigated. Changes in the properties of porous silicon under gamma irradiation were registered by measurements of photoluminescence spectra and Fourier-transform infrared (FTIR) spectroscopy. Besides the appearance of point defects and their subsequent oxidation, the significant differences were shown to be in the behavior of the porous silicon properties in comparison with that of bulk silicon apparently due to the quantum size nature of nanoporous silicon.

Исследование процесса выключения интегрального тиристора импульсом базового тока© И.В

The problem of radiation-produced defects in n-Ge before and after n → p conversion is discussed in the light of electrical data obtained by means of Hall effect measurements as well as Deep Level Transient Spectroscopy. The picture of the dominant radiation defects in irradiated n-Ge before n → p conversion appears to be complicated, since they turn out to be neutral in n-type material and unobserved in the electrical measurements. It is argued that radiation-produced acceptors at ≈E C – 0.2 eV previously ascribed to vacancy-donor pairs (E-centers) play a minor role in the defect formation processes under irradiation. Acceptor defects at ≈E V + 0.1 eV are absolutely dominating in irradiated n-Ge after n → p conversion. All the radiation defects under consideration were found to be dependent on the chemical group-V impurities. Together with this, they are concluded to be vacancy-related, as evidenced positron annihilation experiments. A detailed consideration of experimental data on irradiated n-Ge shows that the present model of radiation-produced defects adopted in literature should be reconsidered.

To increase the maximum power current density of an integrated n+p'Nn'p+-type thyristor during switching-off by a current pulse in the control circuit, the injection of electrons from the n+ emitter should be interrupted before the recovery of the collector p'N junction. This has been done using a rapidly increasing reverse gate current pulse with an amplitude equal to the amplitude of the power switched-off current. After the interruption of the emitter injection, the remaining current through the device is the current of holes extracted from the collector region via the gate electrode. Like in insulated gate bipolar transistors (IGBTs), the physical mechanism that limits the maximum density of the switch-off current is the dynamic avalanche breakdown, which is initiated by the holes extracted through the space charge region of the collector p'N junctions.

A method for measuring the Hall effect in the slow-temperature-drift mode is described. The proposed technique allows measurements of the electrical characteristics of semiconductor materials in a wide temperature range without the necessity to stabilize the sample temperature. This allows one to significantly increase the number of measured points during the experiment in comparison with conventional methods, thus increasing the accuracy of experimental data. The calculation results that were obtained using the electric-neutrality equation on the basis of the experimental data, which were acquired with this method, are in good agreement with those of other authors.

Показано, что взаимодействие протонов с энергией 1 MeV и дозами (0.5-2)·1014 cm-2 с транзисторными структурами с двумерным AlGaN/GaN-каналом (AlGaN/GaN-HEMT) сопровождается не только генерацией точечных дефектов, но и образованием локальных областей с разупорядоченным наноматериалом. Степень разупорядоченности наноматериала оценивалась количественно методами мультифрактального анализа. Увеличение степени разупорядоченности наноматериала, наиболее ярко проявляющееся при дозе протонов 2· 1014 cm-2, приводит к падению подвижности и электронной плотности в двумерном канале HEMT-структур в несколько раз. При этом на транзисторах наблюдается падение величины тока сток-исток и рост тока утечки затвора на порядок. В HEMT-структурах с повышенной разупорядоченностью наноматериала до воздействия протонов, облучение протонами, даже с дозой 1· 1014 cm-2, приводит к подавлению двумерной проводимости в канале и выходу из строя транзисторов.

It has been shown that the interaction of 1 MeV protons at doses of (0.5–2) × 1014 cm–2 with transistor structures having a 2D AlGaN/GaN channel (AlGaN/GaN HEMTs) is accompanied not only by the generation of point defects, but also by the formation of local regions with a disordered nanomaterial. The degree of disorder of the nanomaterial was evaluated by multifractal analysis methods. An increase in the degree of disorder of the nanomaterial, manifested the most clearly at a proton dose of 2 × 1014 cm–2, leads to several-fold changes in the mobility and electron density in the 2D channel of HEMT structures. In this case, the transistors show a decrease in the source–drain current and an order-of-magnitude increase in the gate leakage current. In HEMT structures having an enhanced disorder of the nanomaterial prior to exposure to protons, proton irradiation results in suppression of the 2D conductivity in the channel and failure of the transistors, even at a dose of 1 × 1014 cm–2.