Nitrogen implantation in GaAs1−xPx (x=0.4; 0.65)

Nitrogen ions were implanted in GaAs_1−xP_x (x=0.4; 0.65) at room temperature at various doses from 5×10¹² cm⁻² to 5×10¹⁵ cm⁻² and annealed at temperatures from 600°C up to 950°C using a sputtered SiO₂ encapsulation to investigate the possibility of creating isoelectronic traps by ion implantation. Photoluminescence and channeling measurements were performed to characterize implanted layers. The effects of damage induced by optically inactive neon ion implantation on photoluminescence spectrum were also investigated. By channeling measurements it was found that damage induced by nitrogen implantation is removed by annealing at 800°C. A nitrogen induced emission intensity comparable to the intensity of band gap emission for unimplanted material was observed for implanted GaAs_0.6P_0.4 after annealing at 850°C, while an enhancement of the emission intensity by a factor of 180 as compared with an unimplanted material was observed for implanted GaAs_0.35P_0.65 after annealing at 950°C. An anomalous diffusion of nitrogen atoms was found for implanted GaAs_0.6P_0.4 after annealing at and above 900°C.     

Mg+注入对GaN晶体辐射损伤的研究

在蓝宝石衬底上通过金属有机物化学气相沉积(metal-organic chemical vapor deposition，MOCVD)方法外延生长的GaN薄膜具有良好的结晶品质，χ_min达到2.00%. 结合卢瑟福背散射/沟道(Rutherford backscattering/channeling，RBS/C)和高分辨X射线衍射(high-resolution X-ray diffraction，HXRD)的实验测量，研究了不同剂量和不同角度Mg⁺注入GaN所造成的辐射损伤. 实验结果表明，随注入剂量的增大，晶体的辐射损伤也增大，注入剂量在1×10¹⁵atom/cm²以下，χ_min小于4.78%，1×10¹⁶atom/cm²是Mg⁺注入GaN的剂量阈值，超过这个阈值，结晶品质急剧变差，χ_min达到29.5%；随机注入比沟道注入的辐射损伤大，且在一定范围内随注入角度的增大，损伤也增大，在4×10¹⁵atom/cm²剂量下偏离〈0001〉沟道0°，4°，6°，9°时的χ_min(%)分别为6.28，8.46，10.06，10.85；经过700℃/10min+1050℃/20s两步退火和1000℃/30s高温快速退火后，晶体的辐射损伤都有一定程度的恢复，而且1000℃/30s高温快速退火的效果更好，晶体的辐射损伤可以得到更好的恢复. 关键词： GaN 卢瑟福被散射/沟道 高分辨X射线衍射 辐射损伤     

Effect of implantation temperature on the blistering behavior of hydrogen implanted GaN

GaN epitaxial layers were implanted by 100 keV H⁺ ions at different implantation temperatures (LN₂, RT and 300 °C) with a fluence of 2.5×10¹⁷ cm^?2. The implanted samples were characterized using Nomarski optical microscopy, AFM, XRD, and TEM. Topographical investigations of the implanted surface revealed the formation of surface blistering in the as-implanted samples at 300 °C and after annealing at higher temperature for the implantation at LN₂ and RT. The physical dimensions of the surface blisters/craters were dependent on the implantation temperature. XRD showed the dependence of damage-induced stress on the implantation temperature with higher stress for the implantation at 300 °C. TEM investigations revealed the formation of a damage band in all the cases. The damage band was filled with large area microcracks for the implantation at 300 °C, which were responsible for the as-implanted surface blistering.     

Lattice site location and electronic structure of Te in GaAs

High purity <100> wafers of GaAs were implanted with radioactive^129mTe and stable¹²⁸Te at 110 keV to total doses of 2×10¹⁴ and 2×10¹⁵ Te/cm² respectively and studied with RBS/ channeling and Mössbauer spectroscopy on the 27.8 keV level of¹²⁹I. After implantation and/or annealing at temperatures between 200–300°C the Mössbauer spectra are dominated by a single line. Channeling reveals an appreciable residual damage in the host lattice, but also points to a substitutional position of the Te atoms. After annealing above ≌500°C, where nearly complete lattice damage recovery is obtained, the Te atoms become defect-associated. The results clearly point to the formation of Te_As?V_Ga complexes.     

CW CO2-laser annealing of arsenic implanted silicon

CW CO₂-laser annealing of arsenic implanted silicon was investigated in comparison with thermal annealing. Ion channeling, ellipsometry, and Hall effect measurements were performed to characterize the annealed layers and a correlation among the different methods was made. The laser annealing was done with power densities of 100 to 640 W cm⁻² for 1 to 20 s. It was found that the lattice disorder produced during implantation can be completely annealed out by laser annealing with a power density of 500 W cm⁻² and the arsenic atoms are brought on lattice sites up to 96±2%. The maximum sheet carrier concentration of 6×10¹⁵ cm⁻² was obtained for 1×10¹⁶ cm⁻² implantation after laser annealing, which was up to 33% higher than that after thermal annealing at 600 to 900°C for 30 min.     

Positron annihilation studies of defects in 3CSiC hot-implanted with nitrogen and aluminum ions

2 ⁺ and Al⁺ at temperatures from room temperature (RT) to 1200 °C at doses of 10¹³ and 10¹⁵/cm². It is found from Doppler broadening spectra of annihilation gamma-rays obtained by varying the incident positron energy that hot-implantation gives rise to clustering of vacancies, whereas it suppresses amorphization and diminishes the thickness of damaged layers. The average size of such clusters increases with increasing implantation dose and temperature. Vacancy clustering by hot-implantation can be interpreted by the combination of vacancies during implantation. Vacancy type defects in the low-dose (10¹³/cm²) implanted samples are found to be removed by annealing at 1400 °C, whereas large vacancy clusters still remain after 1400 °C annealing in the high-dose (1 0¹⁵/cm²) implanted samples. It is also derived from the depth profile of positron diffusion length that positron scattering centers are produced after annealing at 1400 °C in all implanted samples. Received: 7 March 1997/Accepted: 6 May 1997     

Annealing characteristics of highly doped ion implanted phosphorus layers in silicon

A combination of sheet resistance, stripping and Hall effect measurements have been made on phosphorus layers implanted into silicon at 40 and 100 keV with doses between 1 × 10¹⁵ and 5 × 10¹⁶ atoms/cm². The implants were made at room temperature and 450°C. After annealing at 650°C, the profile of electrically active phosphorus following a high dose room temperature implant, was found to be flat topped with a concentration of approximately 5 × 10²⁰/cm³. Very little diffusion occurred when annealing to 850°C where the free electron concentration increased to approximately 1.5 × 10²¹/cm³. Highly doped channeled tails were found when implanting at 450°C along the 〈110〉 direction and damage was being continuously annealed out preventing the formation of an amorphous phase. The rapid diffusion of the profile into the bulk found when annealing between 650°C and 850°C was speculated to be due to the presence of a dense dislocation entanglement in these layers following a hot implant.     

Investigation of weak damage in Al0.25Ga0.75As/GaAs by using RBS/C and Raman spectroscopy

The weak damage induced by 0.8 MeV Si ion implantation in the Al_0.25Ga_0.75As films epitaxially grown on GaAs substrates was studied by using Rutherford backscattering spectrometry/channeling (RBS/C) and Raman spectroscopy. RBS/C spectra measured from the implanted samples showed rather low damage level induced by the ion implantation with ion dose from 1×10¹⁴ to 5×10¹⁵ cm⁻². The Raman spectra were measured on these samples. Two kinds of phonon modes, GaAs-like and AlAs-like, are observed, which indicate the existence of multiple phonon vibrational modes in the epitaxial Al_0.25Ga_0.75As films on the GaAs substrate. Compared with the unimplanted sample, the Raman photon peaks for the implanted sample shift gradually to lower energy with the increase of the implantation dose. The strains induced in the implanted layer were also evaluated from the Raman spectra. The result from high resolution double crystal X-ray diffractometry (HRXRD) also verified the evolution of the strains in the implanted layers.     

Behavior of antimony above solid solubility in silicon produced by implantation and laser annealing

Abstract

Antimony implantation into <111> silicon was carried out at RT with a dose of 4.5 × 10¹⁵ cm^?2, energy 75 keV. For the annealing of the sample pulses of a Q-switched ruby laser were used with energy density of ～ 1.5 Joule/cm² and duration of 15–20 nsec. Hall effect measurement was applied to determine the electrical activity of the layers. Lattice location and the depth profile of Sb was studied by RBS and channeling technique. Measurements show that after laser annealing Sb occupies mostly substitutional sites in Si with 84% electrical activity. It has been shown that after laser annealing the concentration of Sb in lattice sites is almost an order of magnitude higher than the limit of solid solubility. Isochron and isothermal annealing of these samples up to 1150°C was carried out to study the kinetics of reverse annealing of antimony.     

Surface damage and topography of erbium metal films implanted with helium to high fluences

Topographical and expansion effects which occur as a result of implanting erbium thin films with helium up to fluences of 1.5 × 10¹⁸ He⁺/cm² are described. There exists an inverse relationship between critical dose and annealing temperature with respect to the formation of surface bubbles. Post implantation annealing at or below 400°C is found to strongly reduce implantation induced expansion for doses less than 3.5 × 10¹⁷ He⁺/cm², but is observed to result in increased expansion above this dose. At temperatures above 400°C, expansion is increased for all doses investigated. Details of bubble development in the implanted layer are discussed and the manner in which surface bubbles develop from enlarged subsurface bubbles is illustrated.     

Ni离子注入多晶ZrO2的表面电性能和结构

对氧化钇(Y₂O₃)部分稳定氧化锆(ZrO₂)样品在室温下进行了Ni离子注入(140kev,5×10¹⁵-2×10¹⁷ios/cm²)和热退火处理.应用电学测量,Rutherford背散射技术(RBS),X射线光电子能谱(XPS)和喇曼光谱方法研究了Ni离子注入多晶ZrO₂的表面电性能,注入层结构及其热退火的影响。     

57Fe conversion electron Mössbauer spectrometric study of boron and carbon ion implanted irons

Amorphous layers produced at the surface of iron by B⁺ and C⁺ implantation (50 kV, 1×10¹⁸ ions cm⁻²) were analyzed by CEMS. The CEM spectrum of B⁺ implanted layer was composed of broad doublet and sextet. Spread hyperfine field distribution, P(H), indicates the formation of extremely disordered FeB layer. Annealing at 400°C brought about precipitation of FeB, which was converted to Fe₂B by annealing at 500°C. The P(H) for C⁺ implanted iron was resolved to 3 subpeaks with H values of 11.0, 18.0 and 22.5 T. The amorphous FeC phase was strongly correlated to crystalline Fe₅C₂ and Fe₂C, which precipitated at 300°C and were transformed into Fe₃C at 500°C. The amorphous layer disappeared by annealing at 600°C.     

Gettering of implanted Au in MeV?C implanted Si

The gettering behavior of 1 MeV?C implantation induced defects for Au (1.5 MeV, 2.2×10¹⁵ cm^-2), implanted into FZ Si(111), has been investigated using Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy. The gettering efficiency of the C implanted layer has been studied as a function of C dose, annealing temperature and time. For a C dose of 2×10¹⁶ cm^-2, a 2 h anneal at 950 °C has been found to result in a gettering efficiency going beyond ?90%. Thermal stability of the gettered Au in the C implanted layer has subsequently been investigated over a temperature range of 950–1150 °C using isochronal annealing. The gettered amount has been found to be stable up to 1050 °C beyond which there is a release. We have observed nanovoids in the C implanted layer surrounded by ?-SiC precipitates along with patches of a-SiC. Up to about 1050 °C, these nanovoids act as efficient gettering centers beyond which they seem to release the trapped Au. Four distinct regimes in annealing temperature with different mechanisms for Au gettering have been observed.     

Damage and lattice location studies in Hg implanted Hg1–xCdxTe

Abstract

Rutherford backscattering (RBS) and ion induced X-ray (PIXE) channeling experiments have been used to study the damage accompanying Hg and Al implantations into Hg_0.8Cd_0.2 Te and its annealing as well as to determine the location of Hg in the crystal.

The damage induced by the implantation of 300 keV Hg and 250 keV Al ions at room temperature was found from RBS channeling studies to reach a saturation level at doses of 1 × 10¹⁴ cm^?2 and 3 × 10¹⁴ cm^?2 respectively. The damage resembles that characteristic for extended defects and it anneals at ≈ 300°C.

The location of the constituents of Hg implanted Hg_0.8 Cd_0.2 Te was studied by PIXE channeling observing the characteristic X-rays for each element. Angular scans indicate that the channels are mostly blocked by Hg atoms for both unannealed and, to a lesser extent, annealed crystals. This observation supports the suggestion that interstitial Hg atoms may be responsible for the conductivity of Hg implanted Hg_1–x Cd_g Te.     

2.0-MeV Er+ implanted in silicon: depth distribution, damage profile and annealing behaviour

Si crystals were implanted with 2.0- MeV Er⁺ at the doses of 5×10¹² ions/cm², 1×10¹⁴ ions/cm², 5×10¹⁴ions/cm², 1×10¹⁵ ions/cm² and 2.5×10¹⁵ ions/cm². Conventional furnace thermal annealing was carried out in the temperature range from 600 °C to 1150 °C. The depth distribution of Er, associated damage profiles and annealing behavioar were investigated using the Rutherford backscattering spectrometry and channelling (RBS/C) technique. A proper convolution program was used to extract the distribution of Er from the experimental RBS spectrum. The obtained distribution parameters, projected range R_p, projected range straggling ΔR_p and skewness SK were compared with those of TRIM96 calculation.The experimental R_p and SK values agree well with the simulated values, while the experimental ΔR_p is larger than TRIM 96 simulated value by a factor of 18%. The damage profile of silicon crystal induced by 2.0-MeV Er⁺ at a dose of 1×10¹⁴ ions/cm² was extracted using the multiple-scattering dechannelling model based on Feldman’s method, which is in a good agreement with the TRIM96 calculation. For the samples with dose of 5×10¹⁴ ions/cm² and more, an abnormal annealing behavioar was found and a qualitative explaination has been given. Received: 11 October 1999 / Accepted: 28 March 2000 / Published online: 5 July 2000     

Nitrogen centers in GaP produced by hot implantation

Backscattering yields of 1.5 MeV?He⁺ ions and low temperature photoluminescence (PL) spectra were measured in GaP crystals implanted with 200 keV?N⁺ ions as functions of ion-dose, temperature during implantation and annealing temperature after implantation. Backscattering results indicate that hot implantation at 500°C greatly reduces radiation damage. The PL intensities of NN lines become maximum in the sample implanted with N⁺ ions of 3 × 10¹⁴cm^?2 at 500°C, and annealed at 1000°C for 1 hr with aluminum glass. The PL intensity is comparable to that of the nitrogen-doped sample during liquid phase epitaxy which is widely accepted as the best method of introducing nitrogen into GaP crystals. In the case of 500°C—hot implantation, the radiation damage produced during implantation is annealed out at 700 ~ 800°C and the implanted nitrogen substitutes for the phosphorous sites after annealing at 900 ~ 1000°C. Some kinds of defects or strains remain around the NN centers even in implanted samples with a maximum PL efficiency. These defects or strains don't seem to reduce the PL efficiency. In the case of room temperature implantation, PL efficiency decreases to one-hundredth or one-thousandth due to the formation of the non-crystalline state compared with hot implantation.     

磷离子注入速率对4H-SiC(0001)晶格恢复与电阻率降低的影响

高剂量的磷离子注入4H-SiC(0001)晶面，注入速率从1.0×1012到4.0×1012 P+ cm-2s-1变化，而注入剂量固定为2.0×1015 P+ cm-2。室温注入，1500oC的高温下退火。利用光荧光和拉曼谱分析注入产生的晶格损伤以及退火后的残余缺陷。通过霍耳测试来分析注入层的电学性质。基于上述测试结果，发现通过减小磷离子的注入速率，极大地减少了注入层的损伤及缺陷。考虑到室温注入以及相对较低的退火温度(1500 oC)，在注入速率为1.0×1012 P+ cm-2s-1及施主浓度下为4.4×1019 cm-3的条件下，获得了非常低的方块电阻106 Ω/sq。     

Controlled surface crystallization of fused silica by Li+-Ion implantation

A new method of producing a glass-ceramic surface layer on fused silica has been demonstrated using Li⁺-ion implantation and relatively low-temperature annealing. Infrared reflection spectroscopy (IRS) was used to study the effects of ion implantation on structural changes. Isochronal annealing of samples implanted with 250 keV Li⁺/cm² brings about a dramatic change in the IRS spectra at 800°C in that it becomes identical with that of α-quartz. The dependence of the degree of crystallization on temperature, Li⁺-ion fluence, and silica type was studied.     

Structural state of III nitride layers implanted with erbium ions

The defect structure of AlGaN/GaN superlattices and GaN layers grown through vapor-phase epitaxy from organometallic compounds is investigated using x-ray diffraction analysis before and after implantation with erbium ions at an energy of 1 MeV and a dose of 3 × 10¹⁵ cm^?2, as well as after annealing. For a superlattice with a total thickness larger than the implantation depth, the satellites of the superlattice region strained under the action of ions disappear in the x-ray diffraction pattern after annealing at temperatures higher than 900°C. This suggests that the radiation-induced defects responsible for the positive deformation in the layer are annealed at these temperatures. However, annealing even at a temperature of 1050°C does not lead to complete recovery of the initial state and the positive deformation in the remaining regions is caused by residual defects. An analysis of the x-ray diffraction patterns demonstrates that, in samples with thin superlattices located at the depth corresponding to maximum radiation damage, the periodic structure that disappears after implantation at a dose of 3 × 10¹⁵ cm^?2 is not recovered even after annealing at a temperature of 1050°C. This inference is confirmed by the results of examinations with an electron microscope.     

The study of damage and optical properties in LiNbO3 implanted by MeV Er and He ions

Abstract

Two LiNbO₃ (X and Y cut) crystals from different companies were implanted by 3.0 MeV Er ions to a dose of 7.5 × 10¹⁴ ions/cm² and 3.5 × 10¹⁴ ions/cm² with different beam current densities, respectively. After annealing at 1060°C in air for 2 hours, one LiNbO₃ sample was implanted by 1.5 MeV He ions to a dose of 1.5 × 10¹⁶ ions/cm². The Rutherford backscattering/channeling and prism coupling method have been used to study the damage and optical properties in implanted LiNbO₃. The results show: (1) the damage in LiNbO₃ created by 3.0 MeV Er ions depends strongly on the beam current density; (2) after annealing at 1060°C in air for 2 hours, a good Er doped LiNbO₃ crystal was obtained; (3) there is waveguide formation possible in this Er-doped annealed LiNbO₃ after 1.5 MeV He ion implantation. It is suggested that annealing is needed to remove the damage created by MeV Er ions before the MeV He ion implantation takes place, to realize the waveguide laser for Er doped LiNbO₃.