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The lattice damage and the nature of the atomic intermixing of Al and Ga induced by As++ implantation and thermal annealing in AlAs/GaAs multiple quantum‐well structures were investigated. The photoluminescence spectra, which show multiple peaks after implantation and annealing, were analyzed based on the shifts of the excitonic peaks arising from quantum wells located at different depths. The depth profiles of intermixing were obtained using a procedure of successive layer‐by‐layer chemical etching followed by photoluminescence measurements. It is found that the atomic mixing is maximum near the sample surface and decreases monotonically with depth, suggesting that the profiles follow more closely the ion induced damage than the ion density. It is also observed that the radiation damage extends beyond 1 μm. Within 0.3 μm from the surface, the damage is relatively heavy and the atomic intermixing increases rapidly with ion dose. Beyond 0.3 μm, the degree of intermixing is only sensitive to the anneal temperature but not to the implantation dose. The results show that both direct collisions and interdiffusion are responsible for the atomic mixing. For the samples implanted with ion doses below 1014 cm−2 and annealed at 650 °C, the optical activation from radiation damage is appreciable. However, the interdiffusion becomes important only at temperatures near and above 800 °C.

Flow cytometry was used to study the lag, exponential, stationary and death phases of non-fixed cultures of Escherichia coli. Fluctuations in the forward angle scatter signal (FALS) were compared with cell size as measured by scanning electron microscopy at low temperature and image analysis. A correlation between FALS and cell size was not observed, although a correlation (r = −0.8) was obtained between FALS and the age of the culture for the first eleven days of incubation. Marked increases in FALS were observed during the lag phase, which were attributed both to changes in size and changes in structure or chemical composition. The distribution of FALS for all culture phases was asymmetric, and was associated with the cell size distribution.

Low-order, monolayer by monolayer (1×1) AlAs/GaAs superlattices grown by MBE using different growth techniques have been studied by X-ray diffractometry. High-resolution multiple-crystal diffractometry was used to study diffraction features near the [004] peaks due to the substrate and epilayers. Using this technique, we have investigated the effect of growth techniques on the strain and tilt of the superlattices. High-resolution X-ray diffraction (HRXRD) results suggest that the sample grown by migration-enhanced epitaxy (MEE) is more highly strained and has more tilt than the same superlattice sample grown using the interrupted growth (IG) technique.

The acquisition of RHEED oscillation information on (100) GaAs substrates is described for use in the growth of “lattice-matched] Iny (AlxGa1−x)1-Y As layers on (100) InP substrates with 0.52 < y < 0.53 and 0.00 < x < 1.00. The observed frequency of the RHEED oscillations on GaAs is the same as on InP, however, the measured lattice parameters of the grown layers are less than that of InP. The x-ray diffraction images show that the misfit dislocations perpendicular to the primary flats of 2” round (100) InP wafers are denser than the parallel ones. Photoluminescence (at 10K) and photoreflectance (at 300K) measurements on a composite layer structure of x=0, 0.2, 0.4, 0.6, 0.8 and 1 clearly show six distinct peaks with narrow FWHMs of less than 20 meV. The measured bandgaps increase linearly with the Al content.

We report the results of our study of controlled interface roughness in low-order GaAs/AlAs superlattices. Samples were prepared using either the interrupted growth or the migration-enhanced epitaxy (MEE) technique. The samples were prepared with m atomic planes of GaAs and m atomic planes of AlAs (m × m) per modulation wavelength and repeated p times. For this study, m = 1 or 3. The samples were studied using X-ray diffraction. The interrupted growth samples both showed a split in one diffraction line indicating layers were not of integral order while the MEE samples showed no splitting, indicating integral order layers.

Differential resistivity and Hall effect measurements and secondary ion mass spectrometry (SIMS) are used to study the annealing behavior of Be-implanted GaAs0.6P0.4. Results similar to that previously reported for Be-implanted GaAs are observed, including outdiffusion of Be into the Si3N4 encapsulant during 900‡C annealing of high dose implants. Nearly all (85–100%) of the Be remaining after a 900‡C, 1/2 hr anneal is electrically active. However, the electrical activation at low annealing temperatures (600–700‡C) is much lower in GaAs0.6P0.4 than in GaAs. A substantial amount of diffusion is observed even for the low fluence Be implants in GaAs0.6P0.4 annealed at 900‡C, indicating a greater dependence of the diffusion on defect-related effects in the ternary.

The performance of semiconductor devices becomes increasingly sensitive to details of the depth distribution of dopants as device dimensions are reduced. In this paper, limitations on the control of dopant distributions resulting from implantation into single‐crystal silicon due to ion channeling are examined for a range of ion atomic numbers and energies characteristic of semiconductor device fabrication. Implantation profiles were obtained by 1 MHz differential capacitance–voltage profiling and by secondary ion mass spectroscopy for silicon substrates implanted at angles from accurately channeled alignment to ’’random equivalent’’ orientation. The critical angle as calculated from an existing computer fit to the Moliere continuum potential was used to scale the angular dependence of the implantation profiles. Ion channeling is seen to have important consequences not only for the deeply penetrating regions of the dopant profile but for the near‐surface profile as well. The results of this study indicate ...

Depth profiles of aluminum and sodium implanted into silicon carbide, silicon and silicon dioxide have been measured by means of sharp resonances in the reactions 27Al(p,γ)28Si and 23Na(p,γ)24Mg. The absolute number of impurity atoms has been determined and compared with that indicated by charge integration during implantation. Adjacent areas of some specimens have been measured by the Cameca ion-beam mass spectrometer and the nuclear resonance method; results are compared. A depth resolution of less than 20 A has been demonstrated for Al very near the surface of SiC. Information concerning the migration of sodium in SiO2 under ion bombardment is presented. Depth profiles are extracted from gamma-ray yield curves taking into account the beam energy distribution, the resonance shape, the average proton energy loss in the sample and the energy loss straggling.

The stoichiometry and contamination of low temperature layers grown by the pyrolytic decomposition of silane in an ammonia‐ and oxygen‐rich atmosphere on and Si substrates are reported. The chemical composition and chemical bonding properties of the films have been analyzed by Auger, nuclear reaction analysis, optical, Rutherford backscattering, and SIMS techniques. Capacitors were fabricated on Si and substrates, and the electrical characteristics were measured. The layers exhibited physical characteristics similar to those of thermally grown layers. Analysis of the films indicated a uniform distribution of Si and O throughout the films. The N concentration measured in the films ranged from 1 to 3% of the O concentration, depending on the growth parameters. The optical results indicated some evidence of small amounts of Si‒N and N‒H bonding. All films grown on Si substrates in the presence of or on substrates had In and Sb contamination throughout, with the In and Sb content increasing from the film/substrate interface to the surface.

Amorphous germanium films were implanted to high boron levels, ∼1021/cm3 peak concentrations. Before and after implantation the conductivity measurements fit the relation logσ∼T−1/4 and no evidence of intravalence absorption was observed indicating that the Fermi level was near the center of the band gap. Thermoelectric power measurements indicated that the samples were weakly n type before implantation and p type after implantation. The position of the fundamental absorption edge shifted to lower energy upon implantation and to higher energies upon subsequent anneals. Implanted recrystallized films were strongly p type, exhibited intravalence absorption, and had very low dc activation energies.

Semi-insulating chromium-doped GaAs was implanted with 100 keV Be ions to fluences of 5 × 1013 and 1 × 1015 ions/cm2. Specimens were annealed at 800°C for thirty minutes. Beryllium atomic concentration profiles, as determined by secondary ion mass spectrometry (SIMS), were compared to the defect density profiles obtained from transmission electron stereomicroscopy techniques for the annealed samples. A major redistribution of Be was observed compared to the as-implanted distribution after annealing at the higher fluence, whereas only a slight redistribution of Be occurred for the lower fluence. A major difference in the defect density profiles was observed with the fluences used for this study in the region where the annealed specimens were compared. The distribution of defects throughout the implanted-annealed layer was examined in GaAs annealed after implantation with the higher fluence using sectioned specimens. The relationships between the atomic Be concentration profile, the defect density profile, and the distribution of some specific defects were compared in these sectioned layers. The distribution and size of defects appear to be directly influenced by the Be concentration and its associated implantation induced damage.

The electrolyte electroreflectance (EER) spectra of AlxGa1−xAs have been obtained in the E0 and E1 regions and for Al concentrations ranging from x=0 to 0.65. From the spectra obtained under low field conditions, the variations of the interband energies with Al concentrations have been established. Following Aspnes [Surf. Sci. 37, 419 (1973)] we have made detailed analyses of the complex resonance line shapes of the experimentally observed modulated reflectance spectra. The parameters Γ and Eg have been calculated and these have been used to generate theoretically the spectra for comparison with experimental results. In addition, we have also examined the effects of dc bias on the EER spectra. Variations of E0, E0+Δ0, E1, and E1+Δ1 have been discussed and results on the line‐shape parameters have been presented.

Atomic profiles of ion-implanted Be and S in GaAs have been measured as a function of implant fluence and annealing temperature. Concentration versus depth profiles were ob-tained by means of secondary ion mass spectrometry (SIMS) techniques. Pyrolytically deposited and sputter-coated Si02 and Si3N4 films were used as encapsulants for the 500 to 900° annealing study. Semi-insulating GaAs was implanted with 200 keV34S+ to fluences of 1 × 1014 and 52× 1014/cm2, and 100 keV9Be+ in the 1 × 1013 to 1 × 1015/cm2 fluence range. The S profiles did not change significantly after annealing at 800°C, although there was some skewing after annealing above 600°C. In contrast, the Be profiles showed significant changes and a decrease in the peak concentration for the ≥ 5 × 10T4/cm2 implants after a 700°C anneal. After a 800°C anneal the Be profile was essentially flat with a monotonic decrease from the surface into the implanted re-gion and a 900°C anneal caused a further decrease in the Be concentration. Profiles of Be implants of ≤ 1 × 1014/cm2 did not change significantly after annealing indicating that the higher fluence cases were related to solubility effects.

Electron spin resonance (ESR), and 71 Ga and 75 As nuclear magnetic resonance (NMR) measurements have been performed on a 20μ thick film of a-GaAs deposited on a SiO 2 substrate by molecular beam epitaxy. The ESR spectrum exhibits the four-line S = 1 2 , I = 3 2 hyperfine pattern characteristic of the singly ionized arsenic antisite defect (As Ga ) commonly observed in crystalline GaAs. The concentration of As Ga centers is estimated to be 10 17 −10 18 cm −3 which is 2–3 orders of magnitude higher than those typically found in as-grown (unirradiated) crystalline samples. 71 Ga and 75 As NMR linewidths suggest substantial quadrupole broadening due to slight deviations from crystalline bonding parameters, but with overall preservation of short-range tetrahedral order.

Secondary ion mass spectrometry (SIMS) has been used with differential resistivity and Hall effect measurements to study the 900°C diffusion of implanted Be in GaAs. Some outdiffusion of Be into the Si3N4 encapsulant occurs for surface Be concentrations above 1 × 1018 cm−3. However, excellent agreement between the electrical and atomic profiles indicates that 85–100% of the Be remaining after annealing is electrically active. The concentration-dependent diffusion observed for implanted Be in GaAs was not significantly altered in experiments using hot substrate implants, two-step anneals, or annealing with Ga and As overpressure.

Chemisorptive luminescence, very similar to that seen by McCarroll [J. Chem. Phys. 50, 4758 (1969)] for oxygen on polycrystalline W, has been observed for oxygen on Si(111) surfaces. It is a diffuse gas‐phase emission extending 2–3 cm above the crystal surface; the spectrum appears continuous, in low resolution, throughout the visible. About 1 in 107 O2 adsorptions produces a photon; no emission is seen during chemisorption of NO, NO2, CO, CO2, and N2. The luminescence decays with hyperbolic kinetics; a model is proposed relating the hyperbolic dependence to the logarithmic rate of surface oxide growth.

Beryllium‐implanted liquid phase epitaxy n‐AlGaAs layers have exhibited p‐n junction behavior after annealing. Graded or abrupt junction behavior was found to be implant fluence dependent. Secondary ion mass spectrometry Be concentration profiles indicate that the graded junctions observed for the higher fluence implants were due to in‐depth migration of Be. Mesa diodes have shown ideality factors of about 2 and avalanche breakdown in reverse bias.

Auger spectroscopy has been used to measure the composition of ion milled GaAs surfaces in ordered and disordered states. Disorder was introduced into GaAs single crystals by implanting Se+ (5×1014/cm2, 100 keV) or Ar+ (5×1016/cm2, 20–100 KeV) ions. Auger composition profiles with 0.5 keV Ar+ ion milling exhibited As‐depleted layers that extended to approximately the depth of the implant region. An enhanced Ar concentration was also seen in the disordered region. These results are compared with similar composition changes in GaAs produced by low energy (

We report boron profiles as determined by secondary ion mass spectrometry that result from implantation into (100) silicon at (0.0±0.1) degrees through various thicknesses of thermally grown silicon dioxide. The implants were performed at room temperature at 150 keV to a fluence of 4.0×1013/cm2. The oxide surface layers examined were 7.6, 33.6, 101.5, or 140.0 nm thick as determined by ellipsometry. The boron profile for implantation through the 7.6‐nm oxide surface layer was only slightly degraded from that seen for accurately aligned implantations into bare (100)‐oriented silicon, while implantation through the three thicker oxides results in profiles similar to those obtained from random equivalent implantations into crystalline silicon. The systematics of the dechanneling of the implanted boron as a function of the thickness of the amorphous surface layer are analyzed and discussed.

Differential resistivity and Hall effect measurements and secondary ion mass spectrometry (SIMS) are used to study the annealing behavior of GaAs doped with high Be concentrations during growth by molecular beam epitaxy (MBE). The diffusion coefficient of MBE‐grown Be in GaAs is determined to be (0.5–1) ×10−13 cm2/sec at 900 °C, a value which is two orders of magnitude lower than that for implanted Be of equal concentration [(2–3) ×1019 cm−3]. The concentration dependence of the diffusion of MBE‐grown Be in GaAs is also observed to be substantially less than that for implanted Be. The implantation of He in Be‐doped MBE layers to create lattice damage does not significantly affect the Be diffusion in a subsequent anneal.

Iron‐doped GaAs layers have been grown by molecular beam epitaxy (MBE) over a substrate temperature range of 460–540 °C with incident 56Fe levels of 2×108–2×1011 atoms cm−2 sec−1. Photoluminescence studies indicate that iron can be incorporated on Ga sites in MBE GaAs. A pronounced accumulation of Fe at the outer epi‐layer surface is observed in secondary‐ion mass spectroscopy profiles of heavily doped samples. This accumulation leads to appreciable donor compensation in n‐type GaAs subsequently grown.

Depth profiles for 60‐keV Al+ implanted in Si have been measured by SIMS analysis as a function of implant fluence and anneal temperature. A pronounced structure has been observed in the annealed profiles for fluences ⩾1015 cm−2. Comparison of the Al profiles with those of implanted B and Ga established that the structure is species dependent. The results of measurements designed to isolate damage effects indicate that the observed structure is induced by the reordering of the amorphous layer.

Uniformly prepared samples have been used for comparison of profiles using three techniques. Proton resonance is nondestructive and provides the best depth resolution at or near the surface. PRP was used as a quantitative standard for total number of particles and for absolute depth. However, the ability of PRP to resolve fine structure beyond the first few hundred angstroms is inferior to SIMS and AES. Proton Resoance Profiling is not expected to be widely used as a profiling technique because of the capital equipment costs and the limited number of impurity-host combination. However, this technique can be utilized to evaluate and calibrate other diagnostic techniques in a quantitative manner. Auger Electron Spectroscopy is a nondestructive surface analysis technique and is most sensitive to surface impurities. In order to profile with AES, the surface must be sputtered, thus destroying the sample. The limits of sensitivity are on the order of 0.1 atomic 7. Thus, the SIMS and PRP techniques are more sensitive for depth profiling of dopants and trace impurities. AES capital equipment costs, however, are signifi'cantly lower than the other two techniques and many surface oriented reliability problems can be effectively examined by AES. Secondary Ion Mass Spectrometry is the most sensitive of the techniques compared in this work and is capable of semiquantitative analysis of a wide range of dopants and impurities relevant to reliability studies. However, as with AES profiling the material is sputtered away thus destroying the sample.

Atomic, optically active, and electrically active profiles measured for 250 keV ion-implanted Be in GaAs as a function of fluence have been correlated. Be atomic depth profiles were obtained by secondary-ion mass-spectroscopy (SIMS) techniques. Photoluminescence and Hall effect measurements made in conjunction with successive layer removal were used to obtain the optically and electrically active profiles. Atomic SIMS profiles obtained from samples implanted to a fluence of 6X10113cm-2 showed no major distribution changes after a 900°C, 30 min anneal treatment. Electrically active profiles obtained from duplicate samples had distributions which were similar to the SIMS results. Hall effect and resistivity measurements after annealing indicated nearly complete electrical activity of the implanted Be, with mobility values typical of p-type bulk material.

The stoichiometry, contamination, chemical bonding, and electrical properties of nitrogen doped, low-temperature SiO 2 films prepared by the pyrolytic decomposition of silane in an ammonia rich atmosphere on InSb and Si substrates have been studied by attenuated total reflection (ATR), Auger, electrical, ellipsometry, nuclear reaction analysis, optical transmission, Rutherford backscattering (RBS), and secondary ion mass spectroscopy (SIMS) techniques. The films were quite similar to thermal SiO 2 films in their physical properties as demonstrated by each of the above techniques and had uniform Si and 0 concentrations. The N concentration in the films was between 1 to 3% of the 0 concentration atomically, depending on growth parameters. The optical results demonstrated conclusive evidence of Si-H bonding but inconclusive evidence of Si-N bonding in the films.