Ion implantation of sulphur into GaAs,GaP and ge monocrystals

The possibility of using ion implantation to form high concentration junctions in semiconductors has been explored for the specific case of sulphur in GaAs, GaP and Ge. The effects of ion dose, ion energy, crystal orientation and target temperature have been investigated by means of radiotracers and sectioning techniques.

It is shown that high concentration junctions can be formed using an incident ion having high electronic stopping cross-section and implanted along the <110< channeling directions of the crystals. A large increase in junction concentration may be obtained when the GaAs and GaP crystals are maintained at 150 °C during the implantation process, but this is not the case with Ge. Rutherford back-scattering of 1 MeV He⁺ ions has been used to measure the ion-bombardment induced damage in the crystals and to show how this damage can be annealed by heating the crystal during the implantation. The annealing, at temperatures up to 150 °C, is most effective in GaAs and least effective in Ge.     

Manifestation of magnetically induced spatial dispersion in the cubic semiconductors ZnTe, CdTe, and GaAs

Nonreciprocal birefringence due to magnetically induced spatial dispersion was observed in the T _d-class cubic semiconductors ZnTe, CdTe, and GaAs near the fundamental absorption edge. The dispersion of the parameters A and g, describing the contributions from terms of the type B _ik_j to the diagonal and off-diagonal components of the permittivity tensor ε _ij(ω,B,k), is determined for ZnTe and CdTe. Analysis of the dispersion and anisotropy of the nonreciprocal birefringence shows that in ZnTe, CdTe, and GaAs, in contrast to magnetic semiconductors of the type Cd_1−x Mn_xTe, it is due excitonic mechanisms. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 7, 514–519 (10 April 1999)     

Molecular mobility, phase transitions and phase transformations in crystalline ortho- and meta-carboranes

The thermally stimulated depolarisation currents (TSDC) technique was used to study the slow molecular mobility in the crystalline forms of highly symmetric polar isomers of carborane. As a consequence of the high molecular symmetry, that originates a molecular shape with a high degree of globularity, plastic crystalline phases with relatively fast reorientational mobility are expected. The TSDC results showed that there is an orientational glass transformation in phase III of ortho-carborane but not in meta-carborane, reinforcing the conclusions of the calorimetric study that suggests that phase III of m-carborane is an orientationally ordered phase. Furthermore, a slow molecular mobility is detected by TSDC in phase II of o-carborane, some degrees below the II→I transition temperature. The mobility in phase II of m-carborane is too fast to be probed by TSDC. It is suggested that the difference in the dynamic behaviour of the two isomers probably arises from their different polarity.     

X ray absorption spectroscopy investigation of phase transition in Ge,GaAs and GaP

Abstract

The phase transitions of GaAs, GaP and Ge under pressure have been investigated by x-ray absorption spectroscopy (XAS). At the onset of the transition the Debye-Waller factor increases and the x-ray absorption near edge structure (XANES) is progressively modified. A mixing of the low and high pressure phase can be determined by XAS as well as amorphization of the sample on pressure release.     

Dimensionally,morphologically, and thermally induced phase transformations in boron-nitrogen nanowires

Structural, thermal, electronic, and energetic properties of cubic boron nitride (BN) nanowires are studied using the density-functional tight-binding method. The effect of the total or partial rearrangement of the cubic structure of nanowires into the hexagonal one depending on the size, morphology, and thermal treatment of the starting wire has been revealed. As distinct from the known homogeneous carbon diamond-like nanowires, stable BN nanowires are two-phase systems whose “shell” has a hexagonal structure and “core” has a cubic structure. The changes in the electronic properties of BN nanowires induced by their structural transformations are discussed. It is shown that boron-nitrogen nanowires can exhibit both semiconducting and metallic properties.     

Temperature-dependent characteristics of a reach-through avalanche photodiode (RAPD) in Ge,Si and GaAs

A theoretical assessment is presented based on a modification of Baraff's theory in order to compare the temperature dependence of several characteristics, including breakdown voltage, excess noise factor, effective ionization rate ratio and efficiency in Ge, Si and GaAs reach-through avalanche photodiodes (RAPD). The temperature coefficient of avalanche breakdown voltage in a depletion region is studied. The response time of a reach-through APD in these materials is also discussed. Finally a comparison of the characteristics between PIN APD and RAPD is presented. The theoretical data have also been substantiated experimentally by Kanedaet al. Supported by National Science Council, the Republic of China     

Electro-optical phenomena accompanying electron and hole heating in superlattices and quantum wells GaAs/AlGaAs and Ge/GeSi

New electro-optical phenomena in quantum-well structures, i.e. modulation of the light absorption and birefringence due to carrier heating in a strong electric field, have been investigated. The effects have revealed different features in the three types of structures under investigation, namely: (1) well-dopedn-type GaAs/AlGaAs multiple quantum wells, (2) barrier-dopedn-type GaAs/AlGaAs superlattices and (3) barrier-dopedp-type Ge/GeSi multiple quantum wells. Possible mechanisms of the phenomena have been discussed.     

Molecular bonding in the conduction states of the Mg2X (X=Si,Ge, Sn) semiconductors

Summary The chemical bond in the electron-deficient semiconductor series Mg₂X (X=Si, Ge, Sn) is analysed in the pseudopotential self-consistent local-density scheme. Hard-core atomic potentials are used to investigate the physical properties of these compounds and to show the regularities peculiar to the periodic table. The ionic character of these materials is studied and related to the scaling electronegativities of their anions. Our results, in good agreement with the experiment, are discussed in order to explain the molecular behaviour of the bonding conduction states.

---

Riassunto Si studia il legame chimico nella serie dei semiconduttori mancanti di elettroni Mg₂X, dove X=Si, Ge e Sn, con il metodo dello pseudopotenziale autocoerente nello schema del funzionale densità locale. Le proprietà fisiche dei composti in esame sono studiate utilizzando potenziali atomici che permettono di evidenziarne le caratteristiche di periodicità. Il carattere ionico di questi materiali è correlato all'elettronegatività degli anioni. I nostri risultati, in buon accordo con l'esperimento, sono discussi in modo da spiegare il comportamento molecolare degli stati di conduzione.

     

压应变Ge/(001)Si1-xGex空穴散射与迁移率模型

应变Ge材料因其载流子迁移率高, 且与硅工艺兼容等优点, 已成为硅基CMOS研究发展的重点和热点. 本文基于压应变Ge/(001)Si_1-xGe_x价带结构模型, 研究了压应变Ge/(001)Si_1-xGe_x空穴各散射概率、空穴迁移率与Ge组分(x)的关系, 包括空穴离化杂质散射概率、声学声子散射、非极性光学声子散射、总散射概率以及空穴各向同性、各向异性迁移率, 获得了有实用价值的相关结论. 本文量化模型可为应力致Ge改性半导体物理的理解及相关器件的研究设计提供有重要的理论参考.     

Temperature dependent characteristics of a PIN avalanche photodiode (APD) in Ge,Si and GaAs

A theoretical assessment is presented based on a modification of Baraff's theory in order to compare the temperature dependence of several characteristics, including breakdown voltage, excess noise factor, effective ionization rate ratio and efficiency in Ge, Si and GaAs PIN avalanche photodiodes. The temperature coefficient of avalanche breakdown voltage in a high field region is studied. Finally the response time of a PIN APD in these materials is discussed.This paper is supported by the National Science Council, the Republic of China.     

Use of the integer and non-integer n-dimensional Debye functions in computing thermal expansivity,with applications to Si and Ge semiconductors

In the present study, a novel method is proposed to accurately calculate the thermal expansivity of semiconductors using the analytical expression obtained for the integer and non-integer n-dimensional Debye functions. The proposed approach is novel as it uses the non-integer n-dimensional Debye functions for the accurate calculations of the thermal expansivities of semiconductors. As an example of the application, the calculation is performed for the thermal expansivities of the Si and Ge semiconductors. Analysis using computer simulation proved that the formula was in excellent agreement with the results reported in the literature.     

Photoionization cross-section and binding energy of donor impurities in GaAs, Ge and Si quantum wires with infinite barriers

Within the effective-mass approximation, we have investigated the binding energies of donor impurities as a function of the wire dimensions and the photoionization cross-section for a hydrogenic donor impurity placed on the center of the quantum well-wire as a function of the normalized photon energy in the GaAs, Ge and Si quantum wires with infinite barriers. The calculations are performed by the variational method based on a two-parametric trial wave function. The results show that the impurity binding energy and the photoionization cross-section depend strongly on both wire dimensions and material parameters.     

Laser-induced damage in InSb at 1.06 μm wavelength—a comparative study with Ge, Si and GaAs

This paper deals with the study of laser-induced damage in n-type single crystal InSb irradiated with a Nd: glass laser of 1.06 μm wavelength and 300 μs pulse duration. Samples of different surface quality were prepared by mechanical lapping and polishing by diamond paste. Evolution of damage morphological features observed at different power densities is discussed. Damage threshold results are analysed in terms of a thermal model taking into account the temperature dependence of various physical parameters and using the finite difference method of calculation. A comparative study of laser induced damage in InSb, Ge, Si and GaAs irradiated under similar conditions is also presented.     

Electron scattering by formic acid in the gas phase: comparing measured and computed angular distributions

Elastic differential cross-sections are measured over a broad range of energy values and the results are compared with quantum calculations for the same process. The agreement between measured and computed data turns out to be fairly good and calculations further allow the separation of the cis and trans conformer behavior and to compare it with the angular distributions for scattering from the dimer at the same energies.     

Pulsewidth-dependence of nonlinear energy deposition and redistribution in Si, GaAs and Ge during 1 μm picosecond irradiation

We have used 1 μm pulses ranging in duration from 4–260 ps to measure the pulsewidth dependence of the nonlinear absorption, melting threshold, and resolidification morphologies of Si, GaAs, and Ge. With these materials, we have been able to quantify a variety of nonlinear absorption processes with a single excitation wavelength. We find that the fluence required to melt Si and GaAs is roughly proportional to the square root of the pulsewidth while that required for Ge is nearly pulsewidth independent. A crystalline-to-amorphous transition is observed in Si for pulses less than 10 ps and in GaAs for all pulsewidths, but no such transition is observed in Ge. These observations are shown to be consistent with the various energy deposition and redistribution mechanisms present in each material. Finally, we have used the active nonlinearities in Si and GaAs to construct optical limiters designed to protect sensitive optical components from intense 1 μm radiation.     

Ion mixing in Al,Si, and their oxides

The redistribution of thin metallic markers due to ion irradiation was studied by backscattering spectrometry in Al, Al₂O₃, Si, and SiO₂. Marker species were selected for their similar masses and different chemical reactivities with the host media and included Ti, Fe, W, Pt, and Au. It was found that the marker signals are Gaussian and that the variance ² of the marker atom distributions increases linearly with the dose of the irradiation, is insensitive to the temperature of irradiation in the range of 80–300 K, and depends linearly on the nuclear stopping power of the incident ions. The absolute values of ² for Ti, Fe, W, Pt, and Au markers in Al and Al₂O₃, W, and Pt in SiO₂ and W in Si is, within±50 %, of 6.5×10³Å² for 300 keV, 8×10¹⁵ Xe ions/cm². These observations suggest that collisional cascade mixing is a dominant mechanism in this type of impurity-matrix combinations. Only Au and Pt in Si mix at a larger rate: ² for Pt is about 3 and for Au about 5 times larger than ² for all other markers. Lower threshold displacement energies and/or the contribution of processes other than cascade mixing are possible considered reasons. In polycrystalline Al, a rapid migration of Au and Pt atoms throughout the Al layer, similar to grain boundary diffusion, is observed.     

Study of irradiation induced changes of electrical and functional characteristics in Ge doped Si diodes

P-on-n diodes fabricated on n-type Cz Si wafers with different Ge doping concentrations were irradiated with 2 MeV electrons and 1 MeV equivalent reactor neutrons using a wide range of fluences and examined by combining current and capacitance transient techniques.     

Optical detection of the breakdown phenomena of integer and fractional quantum Hall effects in GaAs/AlGaAs heterostructures

We have studied photoluminescence (PL) signals from GaAs/AlGaAs heterostructure devices in strong magnetic fields with finite current flowing in the Hall-bar samples. An additional PL peak was found when the current density exceeds the critical value of current-induced breakdown of the quantum Hall effect. This phenomenon gives us the information of heating property of electrons.