Isochronal Annealing Study Research Articles

Formation and annihilation of bulk recombination-active defects induced by muon irradiation of crystalline silicon

Muons are part of natural cosmic radiation but can also be generated at spallation sources for material science and particle physics applications. Recently, pulsed muons have been used to characterize the density of free charge carriers in semiconductors and their recombination lifetime. Muon beam irradiation can also result in the formation of dilute levels of crystal defects in silicon. These crystal defects are only detected in high carrier lifetime silicon samples that are highly sensitive to defects due to their long recombination lifetimes. This work investigates the characteristics of these defects in terms of their formation, recombination activity, and deactivation. Charge carrier lifetime assessments and photoluminescence imaging have great sensitivity to measure the generated defects in high-quality silicon samples exposed to ∼4 MeV (anti)muons and their recombination activity despite the extremely low concentration. The defects reduce the effective charge carrier lifetime of both p- and n-type silicon and appear to be more detrimental to n-type silicon. Defects are created by transmission of muons through the wafer, and there are indications that slowed or implanted muons may create additional defects. In a post-exposure isochronal annealing study, we observe that annealing at temperatures of up to 450 °C does not by itself fully deactivate the defects. A recovery of charge carrier lifetime was observed when the annealing was combined with Al2O3 surface passivation, probably due to passivation of bulk defects from hydrogen from the dielectric film.

Isochronal annealing study of Mg-implanted p-type GaN activated by ultra-high-pressure annealing

Isochronal annealing was performed on Mg-ion-implanted GaN under 1 GPa N2 ambient pressure for 5 min at temperatures of 1573–1753 K. Secondary ion mass spectrometry showed diffusion of Mg atoms and introduction of H atoms during annealing. Deeper diffusion was observed with increasing temperature. From Hall-effect measurements, p-type conductivity was found even for the sample with the lowest annealing temperature of 1573 K. For this sample, the acceptor activation ratio was 23% and the compensation ratio was 93%. The acceptor activation ratio increased to almost 100% and the compensation ratio decreased to 12% with increasing annealing temperature.

Study of defect complexes and their evolution with temperature in hydrogen and helium irradiated RAFM steel using positron annihilation spectroscopy

The formation of hydrogen and helium associated defect complexes and their influence on the nucleation and growth of helium bubbles in Indian Reduced Activation Ferritic/Martensitic steel have been investigated using positron annihilation spectroscopy. Isochronal annealing study has been performed on the samples individually irradiated with H and He ions, and sequentially irradiated with both H and He ions. All the as-irradiated samples show higher S-parameter as compared to the unirradiated sample due to the presence of irradiation-induced vacancy-type defects. Among the single ion irradiated samples, hydrogen irradiated sample shows the presence of H-vacancy complexes having high hydrogen content in the as-irradiated state, an increase in S-parameter due to the release of hydrogen from these complexes at 373 K, and complete defect recovery after annealing at 673 K. The helium irradiated sample shows three distinct stages of annealing; a defect annealing stage with decrease in S-parameter from as-irradiated to 573 K, bubble nucleation stage with a stable S-parameter from 573 to 673 K and the bubble growth region characterized by an increase in S-parameter is observed from 673 to 973 K. Among the sequential irradiated samples, the sample irradiated with helium first and then with hydrogen shows a reduced S-parameter which is due to the saturation of helium-induced vacancies by hydrogen or the formation of H-He-vacancy complexes. Both the sequential irradiated samples show a reduced S-parameter from 573 to 673 K due to the formation of H-He-vacancy complexes under post-irradiation annealing. The nucleation and growth stage of helium bubbles observed under isochronal annealing is independent of the sequence of irradiation. Both the sequential irradiated samples show the bubble nucleation and growth stage similar to helium irradiated sample and further, the presence of hydrogen has no noticeable role in this stage.

Deep level study of beryllium implanted MOCVD homoepitaxial GaN

We present the electrical characterization of point defects detected in beryllium implanted GaN epilayers. We found six majority carrier traps, in the 0.2–1.2 eV energy range below the conduction band edge. An isochronal annealing study was carried out in order to investigate the thermal stability of the detected levels. Most of these possess a high thermal stability up to 1273 K. Their microscopic structures are discussed in the light of the present experimental data and previous reports found in the literature.

The effects of high-energy ion irradiations on the I–V characteristics of silicon NPN transistors

ABSTRACTThe silicon NPN rf power transistors were irradiated with different linear energy transfer (LET) ions such as 50 MeV Li3+, 80 MeV C6+ and 150 MeV Ag12+ ions in the dose range of 1–100 Mrad. The SRIM simulation was used to understand the energy loss and range of these ions in the transistor structure. The different electrical parameters such as Gummel characteristics, excess base current (ΔIB), DC current gain (hFE), displacement damage factor (K) and output characteristics were systematically studied before and after irradiation. The ion irradiation results were compared with 60Co-gamma irradiation result in the same dose range. A considerable increase in base current (IB) and a decrease in hFE and ICSat were observed after irradiation. The degradation in the electrical parameters was comparably very high for Ag12+ ion-irradiated transistor when compared to other ion-irradiated transistors, whereas the degradation in the electrical parameters for Li3+ and C6+ ion-irradiated transistors was comparable with gamma-irradiated transistor. The isochronal annealing study was conducted on the 100 Mrad irradiated transistors up to 500°C to analyze the recovery in different electrical parameters. The hFE and other electrical parameters of irradiated transistors were almost recovered after 500°C for 50 MeV Li3+, 80 MeV C6+ ion and 60Co-gamma-irradiated transistors, whereas for 150 MeV Ag12+ ion-irradiated transistor, the recovery in electrical characteristics is not complete.

A comparison of lower and higher LET heavy ion irradiation effects on silicon NPN rf power transistors

The Silicon NPN rf power transistors were irradiated with 180MeV Au14+ and 150MeV Ag12+ ions in the dose range of 1Mrad to 100Mrad. The SRIM simulation was used to understand the energy loss and range of these ions in the transistor structure. The different electrical parameters such as Gummel characteristics, excess base current (∆IB), dc current gain (hFE), transconductance (gm), displacement damage factor (K) and output characteristics were studied systematically before and after irradiation. These results were compared with lower linear energy transfer (LET) ions such as 50MeV Li3+, 95MeV O7+, 100MeV F8+, 140MeV Si10+ and 175MeV Ni13+ ions in the same dose range. The degradation for 180MeV Au14+ and 150MeV Ag12+ ion irradiated transistors was significantly more when compared to lower LET ions, indicating that the transistors are vulnerable to higher LET ion irradiations. Isochronal annealing study was conducted on the irradiated transistors to analyze the recovery in different electrical parameters. After isochronal annealing, the recovery in hFE and other electrical parameters was around 67% for Ag12+ ion irradiated transistors and 60% for Au14+ ion irradiated transistors.

Evidence for an iron-hydrogen complex in p-type silicon

Interactions of hydrogen with iron have been studied in Fe contaminated p-type Czochralski silicon using capacitance-voltage profiling and deep level transient spectroscopy (DLTS). Hydrogen has been introduced into the samples from a silicon nitride layer grown by plasma enhanced chemical vapor deposition. After annealing of the Schottky diodes on Si:Fe + H samples under reverse bias in the temperature range of 90–120 °C, a trap has been observed in the DLTS spectra which we have assigned to a Fe-H complex. The trap is only observed when a high concentration of hydrogen is present in the near surface region. The trap concentration is higher in samples with a higher concentration of single interstitial Fe atoms. The defect has a deep donor level at Ev + 0.31 eV. Direct measurements of capture cross section of holes have shown that the capture cross section is not temperature dependent and its value is 5.2 × 10−17 cm2. It is found from an isochronal annealing study that the Fe-H complex is not very stable and can be eliminated completely by annealing for 30 min at 125 °C.

Isochronal annealing study of X-ray induced defects in single- and double-walled carbon nanotubes

X-ray induced defects in single-walled (SWCNTs) and double-walled carbon nanotubes (DWCNTs) were characterized by Raman scattering spectroscopy. Frenkel defects, interstitial-vacancy pairs, were revealed to form in both SWCNTs and DWCNTs after X-ray irradiation because these defects were entirely healed by thermal annealing. In order to clarify the structure of the X-ray induced defect in SWCNT and DWCNT, isochronal-annealing experiments were performed on the irradiated samples and the activation energy for defect healing was estimated. The intensity of D band (defect induced band) on Raman spectra was used as a measure of the density of X-ray induced defects. The experimental results were in good agreement with the simulated values using second order reaction model, which indicated that the defect healing was determined by the migration energy of interstitials on the carbon layer. We also found that the activation energy for defect healing of SWCNT and DWCNT were around 0.5 eV and 0.32 eV, respectively. The X-ray induced defects in SWCNTs were more stable than those in DWCNTs. Compared these estimated activation energies to previous theoretical reports, we concluded that bridge and/or dumbbell interstitials are formed in both SWCNT and DWCNT by X-ray irradiation.

Effects of irradiation and annealing on deep levels in rhodium-doped p-GaAs grown by metal-organic chemical-vapor deposition

This paper reports a detailed study of the effects of irradiation and thermal annealing on deep levels in Rh-doped p-type GaAs grown by low-pressure metal-organic chemical-vapor deposition, using deep level transient spectroscopy (DLTS) technique. It is found upon irradiation with alpha particles that, in addition to the radiation-induced defect peaks, all the Rh-related peaks observed in majority, as well as minority-carrier emission DLTS scans show an increase in their respective concentrations. The usually observed α-induced defects Hα1, Hα2, and Hα3 are found to have lower introduction rates in Rh-doped samples, as compared to reference samples (not doped with Rh). Alpha-irradiation has been found to decompose the two minority carrier emitting bands (one at low temperature ∼150 K and the other at ∼380 K) observed prior to irradiation into distinct peaks corresponding to deep levels Rh1 and Rh2 and EL2 and Rh3, respectively. A similar effect is also observed for the majority-carrier emitting band composed of hole emission from deep levels RhA and RhB, which separate out well upon irradiation. Further, from the double-correlation DLTS measurements, the emission rates of carriers from the radiation-enhanced peaks corresponding to deep levels Rh1, Rh2, Rh3, and RhC were found to be dependent on junction electric field. For RhC, the field dependence data have been analyzed in terms of the Poole-Frenkel model employing a 3-dimensional Coulomb potential with q = 2e (electronic charge). Temperature dependence of the hole capture cross-sections of the levels RhA and RhC was also studied quantitatively. The observed dependence of the hole capture cross-section of RhC on temperature can be interpreted in terms of multiphonon capture model, yielding a capture barrier of 0.2 eV and σ(∞) = 2.3 × 10−14 cm2. The results of irradiation and isochronal thermal annealing study, in combination with the theoretical analysis of the field dependence of hole emission data, lead us to interpret the levels RhA and RhB as charged centers and probably complexes of arsenic anti-site defect (AsGa) with Rh-impurity, (AsGa-Rh). The levels Rh1 and Rh2 are also proposed to be complexes, albeit of a different type, of arsenic anti-site defects (AsGa) and Rh-impurity (AsGa-Rh), while the level RhC is likely to be a doubly-charged complex center composed of arsenic interstitial (IAs) and Rh-impurity (IAs-Rh).

Thermal annealing behavior of deep levels in Rh-doped n-type MOVPE GaAs

Abstract We report the results of isochronal annealing study of deep levels in Rh-doped n-type GaAs grown by metal-organic vapor phase epitaxy (MOVPE). Deep level transient spectroscopy (DLTS) technique has been employed to study the effects of annealing on deep levels in Rh-doped p + nn + junction samples. A majority-carrier emitting band of deep levels along with a high temperature peak (RhE1), corresponding to deep level energy position E c −0.92 eV and a minority-carrier emitting band of deep levels are identified with Rh-impurity prior to thermal annealing of our samples. In addition to these Rh-related deep levels, the well-known native defect EL2 at E c −0.79 eV is observed in majority-carrier emission spectra and two inadvertent deep-level defects, H1 at E v +0.09 eV and H3 at E v +0.93 eV, usually observed in reference (without Rh) samples, are also detected in the minority-carrier emission spectra of Rh-doped samples. At least one level is found to be introduced at E c −0.13 eV in Rh-doped samples at about the same temperature position as the level E(A)1, observed in reference samples, as a result of isochronal annealing, while the other two levels observed in reference samples could not be seen in annealed Rh-doped samples. Data on the annealing behavior and other characteristics of both Rh-related bands of deep levels observed in majority- and minority-carrier emission DLTS spectra, as well as for the high temperature Rh-related electron-emission peak, are presented. Possible interpretations of these results for the nature and structure of the different deep-level defects are discussed.

Isochronal annealing study of low energy electron irradiated Al-doped p-type 6H silicon carbide with deep level transient spectroscopy

Al doped p-type 6H silicon carbide was irradiated by low energy electrons to create primary defects. Two deep levels at EV+0.36 eV and EV+0.81 eV were created by this irradiation. Isochronal annealing study was carried out on the electron irradiated sample to investigate the annealing out of the two primary defects and the creation of thermal annealing-induced secondary defects. Four more deep hole traps (0.45, 0.56, 0.74, and 0.71 eV above the valence band) were formed during the whole annealing process up to a temperature of 1600 °C. All the electron irradiated deep level defects were annealed out after the 1600 °C annealing.

Understanding of Carbon/Fluorine Co-implant Effect on Boron-Doped Junction Formed during Soak Annealing

The formation of highly activated ultrashallow junctions is one of the main challenges for the forthcoming generation of complementary metal oxide semiconductor (CMOS) devices. Co-implantation of impurities such as carbon (C) or fluorine (F) is an attractive technique. However, junction optimization can only be achieved with a complete understanding of the underlying physical mechanisms. In this paper, the effect of co-implant on boron (B)-doped preamorphized silicon during the soak annealing is extensively studied. atoms are located in the middle range between the concentration profiles and the end-of-range (EOR) defect band, with the aim of reducing the interactions of dopants with the interstitials released from EOR region. Isochronal annealing study is performed to investigate the impact of codoping on the dopant de/reactivation behavior. It is shown that transient enhanced diffusion can be reduced by both co-implant schemes. The B-doped junction formed with the C co-implant is relatively stable and dopant deactivation is inhibited, while it is presumed that F atoms form complexes, which reduces the B activation level. A physical insight on the dopant-defect interactions associated with co-implant is established through the combination of diffusion and activation studies during soak annealing.

Radiation-Induced Defect Reactions in Cz-Si Crystals Contaminated with Cu

The influence of Cu contamination on radiation-induced defect reactions in n-type Czochralski-grown silicon (Cz-Si) crystals has been studied by means of the Hall effect technique, deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS with supporting theoretical modeling of defects. It is found that the contamination of Cz-Si samples with Cu does not influence significantly the energy spectrum and introduction rates of the principal electrically active defects induced by electron irradiation. The vacancy-oxygen (VO) centre, divacancy (V2) and a complex consisting of a silicon self-interstitial with the oxygen dimer (IO2) are found to be the dominant radiation-induced defects in Cu-contaminated samples as well as in uncontaminated ones. An isochronal annealing study has shown that the presence of Cu affects the annealing behaviour of the vacancy-related defects. In Cu-doped samples the VO centre disappears upon annealing at significantly lower temperatures (175-250°C) compared to those of the VO disappearance in the uncontaminated samples (300-375°C). The disappearance of the VO centres in the Cu-doped samples occurs simultaneously with an anti-correlated introduction of a defect with an energy level at about Ec- 0.60 eV. It is suggested that this defect is formed by the interaction of a mobile Cu atom with the VO complex. According to results of quantum-chemical modelling, in the most stable configuration of the Cu-VO defect a Cu atom occupies a tetrahedral interstitial position nearest to the elongated Si-Si bond of the VO centre. The presence of the Cu atom is found to result in the further elongation of the Si-Si bond and a shift of the VO acceptor level to the middle of the gap. The annealing behaviour of V2 has also been found to be different in the irradiated Cu-doped samples compared to that in the uncontaminated ones. The most probable reason for this difference is an interaction of mobile Cu atoms with di-vacancies. An energy level at about Ec-0.17 eV has been tentatively assigned to a complex consisting of a Cu atom and a di-vacancy.

Properties of dominant electron trap center in n-type SiC epilayers by means of deep level transient spectroscopy

Characterization of dominant electron trap in as-grown SiC epilayers has been carried out using deep level transient spectroscopy. Two electron traps E1 and Z1 at Ec−0.21 and Ec−0.61 are observed, respectively; Z1 being the dominant level. Line shape fitting, capture cross section, and insensitivity with doping concentration have revealed interesting features of Z1 center. Spatial distribution discloses that the level is generated in the vicinity of epilayers∕substrate interface and the rest of the overgrown layers is defect-free. Owing to the Si-rich growth conditions, the depth profile of Z1 relates it to carbon vacancy. The alpha particle irradiation transforms Z1 level into Z1∕Z2 center involving silicon and carbon vacancies. Isochronal annealing study further strengthens the proposed origin of the debated level.

Internal friction study of ion-implantation induced defects in silicon

Using a sensitive silicon paddle oscillator technique, we measured the internal friction of single-crystalline silicon substrate implanted with As +, Si +, B +, and H + ions with a dose of ∼ 1 0 19 m −2. A distinct internal friction peak at about 48 K is observed in all cases. The overall internal friction from 0.4 K to room temperature is also similar for the different species of ions used. The peak shifts to lower temperature at a reduced resonance frequency, characteristic of a thermally activated relaxation. The insensitivity of the peak to the ion species indicates that it is caused by a vacancy-type defect. Isochronal annealing study shows that the peak anneals away at a temperature between 200 and 300 ° C, and that is consistent with divacancy defects. By plasma etching the substrate layer by layer, we have identified that the defects are concentrated at a damaged crystalline layer right underneath the top amorphized layer in the Si + implanted sample. The exact mechanism that caused the relaxation peak is still not clear, although our quantitative analysis points to an electronic origin.

Understanding the role of buried Si/SiO 2 interface on dopant and defect evolution in PAI USJ

For CMOS technology, generations beyond the 65 nm node a major goal is achieving highly activated, ultra-shallow and abrupt profiles. In the case of p-type (boron) implants, one method to achieve this is using Ge preamorphization (PAI) prior to ultra-low energy B implantation. However, for future technology nodes, new issues arise when bulk silicon is supplanted by silicon-on-insulator (SOI). Understanding the strong impact of the buried Si/SiO 2 interface, will enable tests of fundamental models on defect evolution, electrical activation and diffusion. In the present study, boron has been implanted in germanium-preamorphized silicon and SOI wafers. Subsequent to implantation, an isochronal and isothermal annealing study of the samples was carried out. Electrical and structural properties were measured by Hall effect and SIMS techniques. The results show a range of effects in both substrate types, including TED and deactivation driven by interstitials from the end-of-range (EOR) defects. However, in the SOI material there is a lower boron deactivation and the EOR defects are eliminated at a lower thermal budget in SOI than in the bulk silicon due to competition between the upper SOI interface and the Si surface which both act as sinks for interstitials.

Isochronal annealing study of hydrogen interaction with implantation-induced point defects in p-type silicon

Isochronal annealing with zero and reverse bias applied to Schottky diodes was used to monitor the evolution of hydrogen interaction with point defects observed in hydrogen-implanted p-type silicon, i.e., divacancy (VV), carbon–oxygen interstitial pair (C i O i ) and two levels at E v+0.28 and E v+0.50 eV. The VV and C i O i are passivated by hydrogen liberated from hydrogen-containing defects during annealing in the temperature range 90–150°C and reappear upon annealing above 180°C under reverse bias due to hydrogen liberation and its field drift. Two levels at E v+0.50 and E v+0.28 eV are ascribed to irradiation-induced and hydrogen-related defects, respectively.

On defects created in 45 keV H −-implanted n-type Cz Si: a fluence dependence and isochronal annealing study

Five electron traps E1 ( E C=0.17 eV), E2 ( E C=0.22 eV), E3 ( E C=0.29 eV), E4 ( E C=0.43 eV), and E5 ( E C=0.50 eV) were created in n-Si by 45 keV H − implantation. E1 (VO–centre) and E2 (V 2 2−/−) increased linearly with fluence in the range 5×10 10–1×10 12 cm −2, while the hydrogen-related defects E3 (VO–H) and E5 showed a quadratic fluence dependence. E4 also exhibited a quadratic fluence dependence, which could be characteristic of overlapping traps, including VP, V 2 −/0, VH, and V 2H. The ratio E3 : E1 showed sign of saturation at the higher fluences, whereas E5 : E2 increased monotonically with the increasing fluence. E3 and E5 increased with the annealing temperature at the expense of E1 and E2, respectively, up to 200°C, but without a one-to-one correlation. Two secondary defects E6 ( E C=0.20 eV) and E7 ( E C=0.49 eV), which we propose to be higher-order vacancy clusters, were observed above 350°C.

The irradiation and annealing of Si-doped diamond single crystals

Abstract An isochronal annealing study was carried out on electron-irradiated Si-doped high-pressure high-temperature diamonds, measuring PL spectra and the absorption spectra.

The isochronal annealing study on the bias stressed amorphous silicon thin film transistors

The annealing behavior of bias stressed hydrogenated amorphous silicon thin film transistors is studied using the isochronal annealing method. It is observed that the annealing behavior is changed according to the degradation conditions. The isochronal annealing spectra can be decomposed into three annealing peaks (high temperature, intermediate temperature and low temperature peaks). The high temperature peaks and the low temperature peaks are attributed to defect annealing and charge detrapping, respectively. As an origin of the intermediate temperature peaks it is proposed that detrapping of the deeply trapped charges and annealing of the defects in the interface between the undoped amorphous silicon layer and the silicon nitride layer occurs.