Experimental and computer simulation studies of diffusion mechanisms on the arsenic sublattice of gallium arsenide (original) (raw)
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Journal of Applied Physics, 1997
Interdiffusion coefficients on the group V sublattice of GaAs were determined in GaAsP/GaAs and GaAsSb/GaAs superlattices. Strained GaAs 0.86 P 0.14 /GaAs, GaAs 0.8 P 0.2 /GaAs 0.975 P 0.025 and GaAs 0.98 Sb 0.02 /GaAs superlattices were annealed between 850°C and 1100°C under different arsenic vapor pressures. The diffusion coefficient was measured by secondary ion mass spectroscopy and cathodoluminescence spectroscopy. The interdiffusion coefficient was higher under arsenic-rich conditions than under gallium-rich conditions, pointing to an interstitial-substitutional type of diffusion mechanism.
Modeling Diffusion in Gallium Arsenide: Recent Work
MRS Bulletin, 1995
Second to silicon (Si), the most highly developed technology for semiconductor processing exists for gallium arsenide (GaAs). Unfortunately, GaAs processing is more complex than that of Si, mainly because GaAs is a compound semiconductor. Additionally, the lack of a stable native GaAS oxide and other disadvantages relative to Si have prevented this material from expanding beyond the small niche of applications where its high intrinsic electron mobility, superior radiation hardness, and direct bandgap are essential. Adequate understanding and modeling of the process physics are important for extending the “process window” available to GaAs manufacturers and for increasing the appeal of this material. This article deals with one of the most important process events: dopant diffusion.In the next section we briefly describe device-fabrication technology and show the importance of diffusion modeling in the prediction of device characteristics. We then review some elementary diffusion mec...
Identification of vacancy charge states in diffusion of arsenic in germanium
Diffusion of As into Ge from a GaAs overlayer deposited on p-type Ge substrates has been studied by means of secondary ion mass spectrometry. A concentration-dependent diffusion of As atoms was observed in addition to the concentration-independent diffusion of Ga and As atoms. The concentration dependence is explained by a Fermi-level-dependent diffusion model. Arsenic atoms are shown to diffuse through Ge vacancies with the charge states 2- and 0. No presence of the singly negatively charged vacancies was observed, indicating that Ge vacancy could be a negative U center.
Bulletin of Materials Science, 2002
Theoretical studies are carried out to ascertain the dominant mechanism of Si diffusion in GaAs. Lattice dynamical model calculations have shown that the most probable diffusion mechanism is through a single vacancy even though several experiments cannot fix the mechanism as substitutional, substitutionalinterstitial pair or neutral defect pair.
Concentration dependent and independent Si diffusion in ion-implanted GaAs
The diffusion of silicon has been studied in 100 GaAs implanted with 110 16 40-keV 30 Si ions/cm 2. The Si concentration profiles were measured by secondary-ion mass spectrometry and nuclear resonance broadening techniques and the defect distributions by the Rutherford backscattering spectrometry channeling technique. The implanted samples were subjected to annealing in argon atmosphere in the temperature range 650 °C–850 °C. Two independent silicon diffusion mechanisms were observed. Concentration independent diffusion, observed as a broadening of the initial implanted distribution, is very slow and is assigned to Si atoms diffusing interstitially. Concentration dependent diffusion with low solubility and extending deep into the sample is quantitatively explained by diffusion via vacancies of Si atoms in the Ga and As sublattices. Diffusion coefficients together with carrier concentration as a function of Si concentration are given at different temperatures. The solid solubility of Si in GaAs has been determined and an exponential temperature dependence observed. An estimate of the amount of Si atoms residing on either Ga or As sites and the amount of Si Ga-Si As pairs is given. Finally, a fast method is presented for solving the diffusion equation numerically. S0163-18299703331-6
Effect of rapid thermal annealing on carrier lifetimes of arsenic-ion-implanted GaAs
1996
Femtosecond time-resolved reflectivity measurements, structural, and electrical analyses have been performed to investigate the effect of rapid thermal annealing ͑RTA͒ on GaAs implanted with 200 keV arsenic ions at 10 16 ions/cm 2 . Ultrashort carrier lifetimes from 0.48 fs to 2.3 ps were observed for samples annealed at temperatures between 600 and 800°C. The time constants are somewhat shorter than those of RTA-annealed low-temperature molecular-beam epitaxy grown material, while following the same trend of longer time constants and recovery of resistance at higher annealing temperatures. Arsenic precipitates were not observed.
Electrical characterization of arsenic-ion-implanted semi-insulating GaAs
The characteristics of an amorphous GaAs film by implanting dense arsenic ions into semi-insulating GaAs substrate have been studied. The specific contact resistance of the sample at room temperature is found to be 1.1ϫ10 Ϫ1 ⍀ cm 2 . This indicates that the conduction-band electron concentration is less than 10 13 cm Ϫ3 . The activation energy at temperature above 360 K and the density of states are, respectively, 0.6 eV and 10 27 m Ϫ3 eV Ϫ1 as estimated from the slope of Arrhenius plot. Fitting of the Arrhenius plot also suggests that the carrier transport at metal/ semiconductor junction of this material below 360 K is dominated by the variable-range hopping conduction mechanism which depends on deep level defects. © 1994 American Institute of Physics.
Transient enhanced intermixing of arsenic-rich nonstoichiometric AlAs/GaAs quantum wells
The superlattice intermixing of arsenic-rich nonstoichiometric AlAs/GaAs quantum wells grown at lowsubstrate temperatures around 300°C is enhanced by several orders of magnitude relative to diffusion in stoichiometric structures grown at ordinary substrate temperatures. The transient enhanced intermixing is attributed to a supersaturated concentration of group-III vacancies grown into the crystal by low-temperature growth conditions. The enhanced diffusion decays during moderate-temperature annealing between 600°C and 900°C for annealing times between 30 and 1000 s. First-order and second-order decay kinetics were both found to agree equally well with diffusion data obtained from isochronal and isothermal annealing. However, both of these kinetics require a thermally activated annihilation enthalpy to explain temperature-insensitive behavior observed in the time-dependent diffusion coefficient. The activation enthalpy H a for the decay is between 1.4 and 1.6 eV, which is compared with the migration enthalpy H m ϭ1.8 eV of the gallium vacancy in GaAs. For the strongest annealing, the diffusion length approaches the self-diffusion values observed in isotopic superlattices of stoichiometric GaAs. ͓S0163-1829͑99͒03439-6͔ I. TRANSIENT-ENHANCED DIFFUSION
Diffusion and activation of arsenic implanted at high temperature in silicon
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1993
The aim of this work is to study the diffusion behavior and electrical activation of arsenic implanted at high temperatures in silicon. For this purpose, arsenic ions have been implanted into (100) oriented silicon at 180 keV to a dose of 1 X 1Or5 cmm2 at temperatures in the range from 500 to 1000°C. The concentration profiles were measured by secondary ion mass spectrometry. They revealed that there is significant diffusion taking place during the implantation. The diffusion enhancement is considerable, compared to thermal diffusion. Comparisons of the depth distribution of residual defects as revealed by cross-sectional transmission electron microscopy with the concentration profiles were made. It is shown that the anomalous diffusion for implantation temperatures from 500 to 850°C markedly correlates with the depth distribution of the residual defects. For this temperature range, it is also found that the enhancement of arsenic diffusion increases with the implantation temperature, accompanying the decreased formation of the residual defects. However, for implantation temperatures above 850°C the diffusion enhancement reduces with increasing temperature. This can be explained in terms of residual defects acting as sinks for point defects and the suggestion that point defects recombine faster at higher temperatures. The depth distributions of carrier concentration and mobility as examined by differential Hall measurements have shown that changes in carrier concentration and mobility also correlate with the depth distribution of the residual defects, and that the electrical activity increases with the implantation temperature in the temperature range from 500 to 1000°C.
Arsenic induced mass transport of GaAs on V-groove GaAs substrate
Journal of Crystal Growth, 1999, vol. 201-202, pp. 183-186, 1999
ABSTRACT We investigate the effect of As4 over pressure annealing on clean grating profiles aligned along the [011] and [011] directions in a molecular beam epitaxy system (MBE). The grating cleaning is performed using hydrogen radicals or thermal desorption in ultra high vacuum. Subsequent annealing with As4 causes grating deformations with a stronger effect for grating profiles aligned along the [011] direction. This deformation is enhanced after hydrogen radical cleaning and an almost complete planarization is observed for this case. The planarization conditions are determined and we demonstrate that mass transport driven by the arsenic is the principal mechanism for the [011] grating planarization. To our knowledge this is the first report on the deformation of V-groove gratings on GaAs substrate induced by mass transport.