J. L. Benton

Impurity enhancement of the 1.54‐μm Er3+ luminescence in silicon

The effect of impurity coimplantation in MeV erbium‐implanted silicon is studied. A significant increase in the intensity of the 1.54‐μm Er3+ emission was observed for different coimplants. This study shows that the Er3+ emission is observed if erbium can form an impurity complex in silicon. The influence of these impurities on the Er3+ photoluminescence spectrum is demonstrated. Furthermore we show the first room‐temperature photoluminescence spectrum of erbium in crystalline silicon.

Local structure of 1.54‐μm‐luminescence Er3+ implanted in Si

Extended x‐ray absorption fine structure measurements from Er‐implanted Czochralski‐grown Si samples, which exhibit strong luminescence at 1.54 μm, reveal a local sixfold coordination around Er−not of Si−but of oxygen atoms at an average distance of 2.25 A. By contrast, similar concentrations of Er implanted in high purity float‐zone Si samples, which are essentially optically inactive, show that Er is coordinated to 12 Si atoms at a mean distance of 3.00 A.

Microstructure of erbium-implanted Si

A study is presented of the relation between microstructure and 1.54 μm photoluminescence (PL) in high‐energy ion‐implantated Er in Si as a function of implant dose, energy, and temperature and subsequent anneal. Transmission electron microscopy (TEM) of material implanted at 500 keV and ≳100 °C and annealed at 900 °C to activate the Er PL suggests the solubility of Er in Si to be ≊1.3±0.4× 1018 cm−3 at 900 °C. Precipitates take the form of platelets (probably ErSi2) ≊100–300 A in diameter and ≊10 A thick. The 1.54 μm PL saturates at ≊5× 1017 cm−3, before the apparent solubility limit. Layers in which the Si is fully amorphized and subsequently regrown by solid phase epitaxy during an anneal show increased Er incorporation in the crystalline Si but segregation at the amorphous‐crystalline interface. In buried amorphous layers regrown from top and bottom, segregation leads to a line of high Er concentration near the center of the layer: Regrowth from a single interface leads to a segregation pileup of Er a...

Hydrogen passivation of point defects in silicon

Laser melting of crystalline silicon introduces electrically active defects which are observed by capacitance transient spectroscopy. The electrical activity of these point defects is neutralized by reaction with atomic hydrogen at 200 °C.

Interstitial defect reactions in silicon

Deep level transient spectroscopy has been employed in a study of impurity‐interstitial defect reactions in silicon following room‐temperature electron irradiation. Three defects have been isolated and identified from their reactions and electrical properties as Cs‐Ci, Ci‐Oi, and Ps‐Ci. The Cs‐Ci, ME[(0.10), (0.17)] and Ps‐Ci, ME[(0.21), (0.23), (0.27), (0.30)] defects exhibit metastable structural transformations. Our results reveal the multistructural nature and chemical reactivity of the silicon self‐interstitial.

The electrical and defect properties of erbium‐implanted silicon

A detailed study of the electrical and defect properties of ion‐implanted erbium in silicon shows that erbium doping introduces donor states. The concentration of erbium related donors as a function of implant dose saturates at 4×1016 cm−3 at a peak implanted Er‐ion concentration of (4–7)×1017 cm−3. The defect levels related to erbium in silicon are characterized by deep level transient spectroscopy and identified as E(0.09), E(0.06), E(0.14), E(0.18), E(0.27), E(0.31), E(0.32), and E(0.48). The dependence of the photoluminescence on annealing temperature for float zone and for Czochralski‐grown silicon show that oxygen and lattice defects can enhance the luminescence at 1.54 μm from the erbium. Temperature‐dependent capacitance‐voltage profiling shows donor emission steps when the Fermi level crosses EC − ET = 0.06 eV and EC − ET = 0.16 eV.

Oxygen‐related donor states in silicon

Junction spectroscopy techniques have been applied to the study of defect states introduced by heat treatment of silicon containing ∼1018[O]/cm3. Two shallow electron traps are observed, whose concentrations increase with the electron concentration added during a 450 °C anneal. The zero field defect‐state activation energies are E(0.07 eV) and E(0.15 eV). Both states display a Poole‐Frenkel field emission process as expected for donors.

Defect states in electron bombarded n‐InP

A deep level transient spectroscopy study has been made of 1‐MeV electron bombarded liquid encapsulated Czochralski grown n‐InP Schottky barrier structures. Two previously unobserved shallow defect states were found at very low concentration levels in the unirradiated material, and irradiation resulted in seven new states in the upper‐half of the band gap. Introduction rates, electron activation energies, and capture cross sections were examined and a preliminary investigation of annealing behavior was performed. The irradiation induced states all exhibited relatively low introduction rates and large capture cross sections, and three gave evidence of significant defect mobility near room temperature.

THE MECHANISM OF IRON GETTERING IN BORON-DOPED SILICON

High‐energy B implantation was used to introduce gettering layers into float‐zone Si wafers contaminated with 2×1014 Fe/cm3. Secondary ion mass spectrometry shows that about 5% of the Fe contamination is collected at the 4 μm deep peak of a 4×1014/cm2, 3.3 MeV B implant after annealing at 1000 °C for 1 h. Deep level transient spectroscopy demonstrates that increasing the gettering B dose from 4×1012 to 4×1014/cm2 reduces the Fe concentration from 3×1012 to below ∼1010/cm3 in the 1–3 μm deep region from the surface, indicating very efficient gettering. Measurements of the Fe depth profile imply that the depletion of Fe near the gettering layer occurs upon cooling down from 1000 °C. The gettering behavior can be qualitatively understood in terms of a Fermi‐level‐enhanced pairing reaction between Fe and B.

Recombination enhanced defect annealing in n‐InP

The first example of a recombination enhanced defect reaction in InP is reported. The major defect E(0.79 eV) introduced by 1‐MeV electron irradiation of p+n junctions, formed by Zn‐doped epilayers on undoped n‐type substrates, is not observed with Schottky barrier structures on similar material. The defect exhibits a reduction in activation energy of recovery from 1.3 eV under pure thermal annealing to 0.42 eV with minority‐carrier (hole) injection. The enhanced reaction rate is proportional to the square of the injected current showing that the process results from two particle capture.