Study of radiation-induced damage to type III–V semiconductor compounds irradiated with γ quanta and protons using positron annihilation spectroscopy

The effect of proton and ?? radiation on characteristics of the spectra for the angular distribution of annihilation photons (ADAP) have been studied in the case of positron annihilation in GaAs and GaP single crystals. Relative variations in defect accumulation and annealing under irradiation and subsequent isochronous annealing of the samples have been studied using variations in the basic parameters of the ADAP spectra. In both cases (GaAs and GaP), the variations in the ADAP spectral parameters as functions of the annealing temperature have a steplike character, which is interpreted as the formation of a certain type of defects with different annealing activation energies.     

Defects in semiconductors observed by positron annihilation

The origin of the effect of defects on positron annihilation in semiconductors has been studied. The electron-positron momentum densities in elemental semiconductors (Si and Ge), III-V compound semiconductors (GaAs, InP and GaSb), diamond and the proton irradiated Si were investigated by a full-scale use of the two-dimensional angular correlation of positron annihilation radiations (2D-ACAR). The obtained results showed, as a whole, good agreement with the electron momentum distribution of the fully occupied Jones zone with a small exception for the fact that the low density channels are running along the three principal axes. This anisotropy was strong in elemental semiconductors, while it was weakened in compound semiconductors. This anisotropy and its dependence on the material were found to be generally understood by the incorporation of crystal symmetry. The anisotropy will be discussed by group theory in conjunction to the effect of defects on positron annihilation.     

Impurity effect on the creation of point-defects in GaAs and InP investigated by a slow positron beam

The impurity effect on the creation of point-defects in 60-keV Be⁺-ion implanted GaAs and InP has been studied by a slow positron beam. Vacancy-type defects introduced by ion implantation were observed in n-type GaAs. For p-type GaAs, however, this was not the case. This can be attributed to the recombination of vacancy-type defects with pre-existing interstitial defects in p-type GaAs. In the case of InP, the vacancy-type defects were created by ion implantation and increased with the implantation dose. However, no significant doping effect was observed in InP.     

Time-resolved defect production and annealing during electron-beam processing of silicon

In (100)p-Si radiation damage was produced by implanting B⁺ ions with an energy of 80keV, 90keV and 1.6MeV. The specimens were annealed by scanned electronbeam irradiation (20keV, 1–2mAcm^–2). The formation, evolution and annihilation of defects during the irradiation process were investigated by employing DLTS and RBS measuring techniques. The results show a minimum of defect concentration and an efficiency of the electrical activation of B higher than 80% at an annealing time of 4.5 s. For irradiation times longer than 5 s it becomes evident, that the crystal surface acts as source of defects and contributes to an increase in defect concentration.     

100 keV质子辐照对空间GaAs/Ge太阳电池光电效应的影响

利用空间环境模拟设备,用固定能量为100keV、注量为1×10⁹—3×10¹²cm^-2的质子,对空间实用GaAs/Ge太阳电池进行了辐照试验.利用伏安(I-V)特性、光谱响应和光致发光(PL)光谱测试,研究分析了电池的光电效应.试验表明,电池的各种电性能参数如短路电流(I_sc)、开路电压(V_oc)、最大输出功率(P_{m< 关键词： GaAs/Ge太阳电池 质子辐照 光电效应}     

III-V族化合物半导体材料的高能重离子辐照效应

用高能（５００ＭｅＶ）Ｎｅ离子束对ＧａＡｓ和ＩｎＰ进行了辐照，用ＭｏｎｔｅＣａｒｌｏ模拟、正电子湮没谱学以及红外光谱研究了辐照产生的缺陷特性．结果表明，在未辐照的样品中存在单空位，经辐照后，可在样品中产生单空位；当剂量较大时，还会形成双空位甚至尺寸较大的空洞．红外光谱测量发现，在辐照后的ＧａＡｓ样品中有非晶区形成．此外，辐照在样品中还产生了反位缺陷ＧａＡｓ和ＩｎＰ以及受主杂质ＺｎＩｎ．对经１０１４ｉｏｎｓ／ｃｍ２剂量辐照的ＩｎＰ进行了光学实验，在辐照后的ＩｎＰ材料中发现了亚稳态中心． Both GaAs and InP were irradiated by high energy (500 MeV) Ne ions. The Monte Carlo simulation, positron annihilation and IR spectroscopy were used to study the radiation induced defects. The result showed that monovacancies existed in as grown samples, but more monovacancies were introduced, after Ne ions irradiation, and with increasing radiation dose, divacancies were formed, and eventually large voids were observed. The IR measurement for irradiated GaAs samples confirmed the...     

GaInP/GaAs/Ge三结太阳电池不同能量质子辐照损伤模拟

以GaInP/GaAs/Ge三结太阳电池为研究对象,开展了能量为0.7, 1, 3, 5, 10 MeV的质子辐照损伤模拟研究,建立了三结太阳电池结构模型和不同能量质子辐照模型,获得了不同质子辐照条件下的I-V曲线,光谱响应曲线,结合已有实验结果验证了本文模拟结果,分析了三结太阳电池短路电流、开路电压、最大功率、光谱响应随质子能量的变化规律,利用不同辐照条件下三结太阳电池最大输出功率退化结果,拟合得到了三结太阳电池最大输出功率随位移损伤剂量的退化曲线.研究结果表明,质子辐照会在三结太阳电池中引入位移损伤缺陷,使得少数载流子扩散长度退化幅度随质子能量的减小而增大,从而导致三结太阳电池相关电学参数的退化随质子能量的减小而增大.相同辐照条件下,中电池光谱响应退化幅度远大于顶电池光谱响应退化幅度,中电池抗辐照性能较差,同时中电池长波范围内光谱响应的退化幅度比短波范围更大,表明中电池相关电学参数的退化主要来源于基区损伤.     

Electrical characterization of defects introduced in n-GaAs by alpha and beta irradiation from radionuclides

We investigated defect production in n-type GaAs with two different free-carrier densities (4×10¹⁴ and 1×10¹⁶/cm³) by using particles liberated from radionuclides. ⁹⁰Sr and ²⁴¹Am were employed as beta and alpha sources, respectively. The results obtained for electron irradiation showed that the same set of primary defects can be produced by beta irradiation from the Sr source as by electrons produced in an accelerator. Similarly, the defects produced by alpha irradiation from the Am source closely resemble those introduced by alpha irradiation in a Van de Graaff accelerator. It was found that the relative concentrations of the primary defects in electron-irradiated GaAs are different to those in alpha-particle irradiated GaAs. Further, for the first time, an alpha irradiation induced defect which seems to be related to the doping concentration was observed in the 10¹⁶/cm³ Si doped GaAs. It is concluded that the use of radionuclides is an inexpensive and convenient method to introduce and to study radiation induced defects in semiconductors.     

双束质子辐照砷化镓光电导探测器的I-V特性

 对用能量为7.5MeV和20MeV,注量为10¹¹～10¹³cm^-2的质子辐照后的砷化镓材料制作的光电导探测器的光电流和暗电流进行了测试，并由此推得电导率的变化。结果表明，经过能量为7.5MeV的质子改性后的砷化镓探测器相对于未改性的附加光电导率Δσ减少，而且随着辐照注量的增加而越小，而对于先用能量为20MeV质子辐照后再用能量为7.5MeV的质子辐照的砷化镓材料制作的探测器，其附加光电导率Δσ的减少则更为明显。对上述现象进行了分析，并根据其相应关系预测了该种探测器的响应时间、灵敏度、拖尾现象及受X射线激发的输出脉冲的后延的变化情况。     

Study of the effect of annealing on defects in Fe-Mn-Si-Cr-Ni-C alloy by slow positron beam

FeMnSi shape memory alloys (SMAs) have received much attention as one-way SMAs due to their cost-effectiveness. Variable-energy (0-30 keV) positron beam studies have been carried out on a Fe-Mn-Si-Cr-Ni-C alloy with different degrees of deformation. Doppler broadening profiles of the positron annihilation as a function of incident positron energy were shown to be quite sensitive to defects introduced by deformation. The variation of the nature and the concentration of defects are studied as a function of isochronal annealing temperature. These results are correlated with the data measured with the positron annihilation lifetime spectroscopy (PALS). The positron annihilation results are compared to XRD and optical microscopy (OM).     

The Effect of Point Defects on the Activation Processes in Semiinsulating GaAs Irradiated by Si28 Ions

The layered concentration, concentration profile, and mobility of electrons in the Si²⁸ ion-implanted layers (IIL) of semiinsulating GaAs are investigated. The specific resistance of the latter is also studied upon radiation annealing (RA) in the temperature range 590–800 °C using electron energies higher than the threshold energy of defect formation. The IIL are shown to form during RA at much lower temperatures. The layers exhibit high electrical activation of Si²⁸ ions, with the electron-concentration profile corresponding to the calculated one, and a low concentration of residual defects limiting the electron mobility. The radiation annealing increases the resistance of semiinsulating GaAs. The calculations show that these effects are due to the Frenkel pairs (FP) generated by radiation. A high degree of ionization of GaAs atoms significantly reduces energies of potential barriers of diffusion, FP recombination, and electrical impurity activation.     

正电子湮没谱和光致发光谱研究掺锌GaSb质子辐照缺陷

用正电子湮没谱和光致发光谱研究了质子辐照后掺锌GaSb中的缺陷.通过分析正电子的缺陷寿命τ₂及强度I₂的变化发现,在高能质子的辐照下产生了双空位缺陷V_GaV_Sb,可能同时产生了小的空位团.正电子平均寿命τ_av和S参数随着质子辐照剂量的变化也证明了这一结论.通过分析不同质子辐照剂量下掺锌GaS     

Proton radioactivity of151Lu

A (1231±3) keV proton activity has been observed in the fusion reaction⁵⁸Ni +⁹⁶Ru→¹⁵⁴Hf^*. The production cross section peaks at 50 MeV of excitation energy with a value of about 70 μb. No coincidences with annihilation radiation or withK X-rays could be observed. The activity is assigned to direct proton decay of the new isotope¹⁵¹Lu. The measured half life is (85±10) ms.     

Localization of carbon atoms and extended defects in silicon implanted separately with C+ and B+ ions and jointly with C+ and B+ ions

The possibility to control the localization of implanted carbon in sites and interstices in silicon immediately during the implantation has been demonstrated. The formation of residual extended defects in silicon implanted separately with C⁺ and B⁺ ions and jointly with C⁺ and B⁺ ions has been shown. It has been found that the formation of residual defects can be suppressed due to annihilation of point defects at C atoms (the Watkins effect). The positive effect is attained if implanted carbon is localized over lattice sites, which is provided by its implantation with the effective current density of the scanning ion beam no lower than 1.0 μA cm^?2.     

Divacancy complexes induced by Cu diffusion in Zn-doped GaAs

Positron annihilation spectroscopy was applied to investigate the nature and thermal behavior of defects induced by Cu diffusion in Zn-doped p-type GaAs crystals. Cu atoms were intentionally introduced in the GaAs lattice through thermally activated diffusion from a thin Cu capping layer at 1100 °C under defined arsenic vapor pressure. During isochronal annealing of the obtained Cu-diffused GaAs in the temperature range of 450?850 K, vacancy clusters were found to form, grow and finally disappear. We found that annealing at 650 K triggers the formation of divacancies, whereas further increasing in the annealing temperature up to 750 K leads to the formation of divacancy-copper complexes. The observations suggest that the formation of these vacancy-like defects in GaAs is related to the out-diffusion of Cu. Two kinds of acceptors are detected with a concentration of about 10¹⁶ ? 10¹⁷ cm^?3, negative ions and arsenic vacancy copper complexes. Transmission electron microscopy showed the presence of voids and Cu precipitates which are not observed by positron measurements. The positron binding energy to shallow traps is estimated using the positron trapping model. Coincidence Doppler broadening spectroscopy showed the presence of Cu in the immediate vicinity of the detected vacancies. Theoretical calculations suggested that the detected defect is V _Ga V _As-2Cu_Ga.     

Proton radiation effect on GaAs/AlGaAs core–shell ensemble nanowires photo-detector

We demonstrate that the GaAs/AlGaAs nanowires(NWs) ensemble is fabricated into photo-detectors. Current–voltage(I–V) characteristics are measured on Ga As/Al Ga As core–shell ensemble NW photo-detectors at room-temperature before and after 1-MeV proton irradiation with fluences from 1.0 × 10~(13) cm~(-2) to 5.0 × 10~(14) cm~(-2). The degradation of photocurrent suggests that the point defects induced by proton radiation could cause both carrier lifetime and carrier mobility to decrease synchronously. Comparing with a GaAs quantum well, the degradations of light and dark current for the irradiated NWs photo-detector indicate that NWs material is a preferable potential candidate for space applications.     

Contact welding study of carbon nanotube with ZnO nanowire

Study of proton beam induced welding of multiwall carbon nanotubes (MWCNTs) with ZnO nanowires (NWs) has been carried out by proton (H⁺) beam irradiation. The samples were irradiated by 70-keV proton (H⁺) ion beams at different substrate temperatures. The irradiation-induced defects in CNTs and ZnO NWs were greatly reduced at elevated temperature. The crystalline structure of ZnO NWs and MWCNTs were found to remain stable after the irradiation at 700 K. As a preparation step, a coupling of two parallel ZnO NWs with irradiation has also been demonstrated. The welding mechanisms of MWCNTs and ZnO NWs were also been suggested. These two welding processes between same and distinct nanostructures to form homo- and hetero-junctions have provided an opportunity to mass produce interconnecting one-dimensional structures used for the manufacturing of future nanowire-based electronic circuits and devices.     

Ordering of crystal structure by ionizing radiation

We have studied the action of ionizing radiation on defect-containing semiconductor crystals, metals, and alloys. Using modern methods for investigation of solids, Rutherford back scattering of channeled charged particles, x-ray diffraction, electron microscopy, and also calorimetric methods, we have established: a) irradiation (by x-ray beams, gamma rays, and electrons) of metals and alloys with an equivalent radiation dose less than 10⁵ J/kg and of semiconductor crystals with a dose less than 10³ J/kg does not lead to additional accumulation of defects but conversely leads to elimination of defects and transition of the crystal to a more equilibrium state; b) ionization processes play a determining role in rearrangment of defects in crystals exhibiting both semiconductor and metallic conductivity. We show that rearrangment of the crystal occurs as a result of stored energy in the crystal which is liberated due to chain reactions of annihilation of defects, initiated by ionization. Transition of the crystal to the equilibrium state is accompanied by improvement of its physical properties.Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 58–67, December, 1994.     

Positron annihilation studies in alpha-irradiated n-type GaAs

The positron annihilation technique has been used to study the recovery of defects in α-irradiated n-type GaAs. The Doppler broadening lineshape parameter, S, showed, for the first time, the recovery in three steps beginning around 120°C, 300°C and 510°C indicating the presence of three types of defects.     

Defects in electron-irradiated 3C-SiC epilayers observed by positron annihilation

Positron annihilation has been used to study defects induced by 1 MeV electron irradiation in cubic silicon carbide (3C-SiC) epitaxially grown on Si substrates by chemical vapor deposition. Narrowing of the Doppler-broadened energy spectrum of annihilation gamma-rays by the electron irradiation was observed in the fluence range above 5 × 10¹⁶ e/cm². The electron fluence dependence of the narrowing is accounted for by the introduction of monovacancies and divacancies in 3C-SiC by the irradiation.