No abstract

Gallium arsenide has been implanted with nitrogen ions at 1–3 MeV and fluences between 3.3×1013 and 2.0×1017 ions/cm2. Room-temperature infrared spectra are presented which show major changes in the reststrahl region. A sample having the highest fluence was isochronally annealed with 2-h 100°C steps from 200 to 600°C, and the implantation-induced reflectivity changes are annealed by 600°C. Changes of the dispersion parameters were determined by Kramers-Kronig analysis as well as by curve fitting with classical dispersion (CD) analysis. Examples of dispersion parameters obtained by different analyses are compared and their validity is discussed. The data of nonimplanted and samples implanted with fluence up to 3.3×1014 ions/cm2 can be satisfactorily fitted with CD analysis assuming the material to be optically homogeneous. With this assumption, attempts to fit the data of samples with fluences ≥3.3 ×1015 ions/cm2 were unsuccessful. By extending the CD analysis to a layer model a reasonable fit was achieved. The analyses indicate changes in the transverse- and longitudinal-optic-mode frequencies. The latter changes were confirmed by Raman scattering measurements. Both the analyses and interference fringes observed in the near-infrared reflection spectra indicate some implantation-induced increase in the high-frequency dielectric constant.

The lattice defects in heavily silicon-doped gallium arsenide crystals grown by the horizontal Bridgman method were examined as a function of heat treatment and silicon concentration by using transmission electron microscopy. The substructure of as-grown crystals, containing =4 x l O l 9 Si/cmS exhibited the presence of numerous extrinsic stacking faults lying on t h e { 111) and small vacancy type prismatic dislocation loops lying parallel t o the { 110) planes of GaAs. Annealing these crystals at 1100 "C for 15 minutes and quenching to room temperature caused the disappearance of both types of defects and produced a homogeneous solid solution. However, a second heat treatment of the homogenized samples a t temperatures in the range GOO to 850 "C produced additional prismatic dislocation loops, the size, concentration and distribution of'which exhibited an anomalous temperature dependence. More lightly Si-doped [(Si) N 1 x 101scm3] and undoped GaAs crystals grown by the Bridpman method did not exhibit the presence of prismatic dislocation loops or extrinsic stacking faults when subjected to heat treatments similar t o those mentioned above. However, annealing of the lightly doped crystals a t 750 "C for 100 hours resulted in the formation of helical dislocations. The origin of the lattice defects observed in Si-doped GaAs and their behavior during various annealing treatments are discussed and the role of silicon in defect production and annealing is delineated.Die Gitterstorungen in stark mit Si dotierten Galliumarsenid-Kristallen, die nach der horizontalen Eridgman-Methode gezogen wurden, werden in Abhangigkeit von der Temperung und Siliziumkonzentration mit Transmissions-Elektronenmikroskopie untersucht. Die Substruktur der unbehandelten Kristalle, mit ~4 x 1018 Si/cm3 zeigt die Anwesenheit von zahlreichen durch Fremdstorungen verursachten Stapelfehlern auf den { 11 1) -Ebenen und kleinen prismatischen Versetzungsschleifen vom Leerstellentyp, parallel zu den { 110) -Ebenen von GaAs. Das Tempern dieser Kristalle fur 15 Minuten bei 1100 "C und Abschrekken auf Zimmertemperatur verursacht das Verschwinden von beiden Defekttypen und ruft eine homogene feste Losung hervor. Jedoch verursacht eine zweite Temperung der homogenisierten Proben bei Temperaturen im Bereich von 600 bis 850 "C zusltzliche prismatische Versetzungsschleifen, deren GroBe, Konzentration und Verteilung eine anomale TemperaturabhLngigkeit zeigt. Schwacher Si-dotierte (Si = 1 x 101*/cm3) und undotierte GaAs-Kristalle nach der Bridgmanmethode zeigen nicht die prismatischen Versetzungsschleifen oder durch Fremdstorstellen verursachten Stapelfehler, wenn sie ahnlichen Temperungsverfahren unterworfen werden. Jedoch verursacht eine Temperung leicht dotierter Kristalle von 100 Stunden bei 750 "C die Bildung von Schrauben-Versetzungen. Die Ursache der Gitterdefekte, die in Si-dotiertem GaAs beobachtet werden, und ihr Verhalten wahrend verschiedener Temperungsverfahren werden diskutiert und die Rolle des Siliziums bei der Hervorrufung der Defekte nnd der ...

Room-temperature near-infrared reflection and transmission measurements on GaAs ion implanted at 2.7 MeV with a fluence of 6.4×1016 P+/cm2 showed amplitude-modulated interference fringes. The reflection fringes were analyzed by using a simple model in which the implanted material is approximated by two partially absorbing layers on a nonabsorbing substrate. The analysis results indicate that the effective layer thicknesses are comparable with those predicted by the projected ion range and the width of the Gaussian ion distribution. The implantation-induced damage produces an increase in the refractive indices. The observed increase in the absorption is similar to that previously reported for GaAs which has been implanted at lower energy.

Near normal incidence reflection and transmission measurements of GaAs and GaP samples implanted with large doses of ∼3-MeV ions of 31P+ or 14N+ showed frequency-dependent maxima and minima in the frequency range 800≲ν≲7500 cm−1. Assuming a layer model for the implanted material and considering reflections from layers surfaces, the interference fringes are analyzed to obtain the refractive index and thickness of both the cover and buried layers and substrate. With the same layer model the changes in the GaAs reststrahlen are shown to be quantitatively compatible with the results of the fringe measurements. Annealing GaAs at temperatures ≲400 °C reduced the implantation-induced changes in the refractive index but the layer thicknesses remained constant. There was no evidence for regrowth by motion of the implant-substrate interface as has been reported for silicon crystals. The analysis of the reststrahlen data for GaP is less satisfactory since the data could not be closely fitted with any choice of parameters.