Zn Ion Implantation Research Articles

Amorphization and crystallization in high-dose Zn+-implanted silicon

The nature of amorphization and crystallization of Si brought about by 50 keV Zn ion implantation within the dose range 2×1017–1×1018 cm−2 is studied. The structures are evaluated in the as-implanted state by transmission electron microscopy, transmission electron diffraction, reflection high-energy electron diffraction, selected-area electron diffraction, x-ray energy-dispersive analysis, and Rutherford backscattering spectrometry. It is found that, contrary to the theoretical predictions, the Zn concentration profile does not reach saturation even at a dose as high as 1×1018 cm−2. A common feature of the microstructure of these high-dose implants is the formation of a continuous amorphous layer and concurrent crystallization of Zn and Si in small crystalline clusters. Microscopic beam-heating effects are also believed to play an appreciable role in the development of the specific morphologies observed. The results are interpreted in terms of two recent models proposed in the literature and the concept of critical dose ranges.

Effects of p-type dopants on enhancing AlAs/GaAs superlattice disordering

It is quantitatively shown that the mechanism reponsible for enhancing AlAs/GaAs superlattice disordering by the p-type dopants Zn and Be is essentially the Fermi-level effect occurring in Garich crystals. In the abundance of holes, the Fermi-level effect increases the concentration of the doubly-positively-charged group III element selfinterstitials (designated as I Ga 2+), which govern Al-Ga interdiffusion in crystals rich in group III elements. Under Zn (or Be) indiffusion and ion implantation conditions, the crystal portion where the enhanced Al-Ga inter-diffusion occurs has become rich in group III elements irrespective of whether the annealing ambient is As rich or poor. This is because the incorporation of the Zn (or Be) atoms onto the group III sublattice site will naturally produce crystals rich in group III elements. In the Asrich annealing ambient cases, only the crystal surface region becomes rich in As, while the superlattice disordering reaction occurs in the deeper Zn (or Be) diffusion front region, which is rich in group III elements.

High Energy Si, Zn and Ga Ion Implantation into GaAs on Si

High Energy Si, Zn and Ga Ion Implantation into GaAs on Si

Ultra-Thin p+ Layers in GaAs

AbstractThe formation of shallow (0.05–0.2 μm) p+ layers in GaAs by pulse diffusion of Zn from a doped oxide source, thermal diffusion of Cd by vapor transport, or by low energy implantation of Cd, Mg, Be, Zn or Hg ions was investigated by electrochemical capacitance-voltage profiling, Secondary Ion Mass Spectrometry, Rutherford backscattering and Hall measurements. Hole densities in excess of 1019 cm−3 are obtainable by either Zn diffusion or acceptor implantation, though the high temperature cycle must be kept to ≤3 sec at (≤1000°C to prevent excessive redistribution of the acceptor dopants. Pulse diffusion at temperature °C leads to shallow regions with atomic concentrations above 1019 cm−3, but electrically active concentrations orders of magnitude less. These results are explained in terms of the unavailability of a sufficient density of vacancies at low temperatures.

Shallow p+ layer in GaAs formed by zinc ion implantation

A shallow p+ layer with a steep boundary was obtained by Zn ion implantation and a capless annealing in an arsenic ambient. A capped annealing with a plasma deposited Si3N4 film resulted in a carrier concentration profile broadened by the diffusion enhanced by the interfacial stress between the capping film and the semiconductor. The p+ layer had a peak carrier concentration of 8×1019 cm−3 and a thickness of less than 1000 Å. Arsenic pressure in the annealing ambient also suppressed the enhanced diffuison of Zn in the ion-implanted GaAs.

GaAs1-xPx Light Emitting Diodes Produced by Zn Ion Implantation. I. Dose Dependence of Properties of Implanted Diodes

Properties of GaAs1-xPx light-emitting diodes produced by Zn ion implantation have been investigated as functions of ion dose. The luminescence efficiency of the implanted diode peaks at a dose of around 4∼8×1015 cm-2 and exceeds more than twice that of conventional thermally diffused diodes. The implanted diode has a p+ -p- -n structure in contrast to the p+ -n structure of the diffused diode, and the width ratio (p-/p+) decreases as a function of the logarithm of the ion dose. The width of the depletion layer and the breakdown voltage of the implanted diode are larger than those of the diffused diode and decreases with increasing ion dose. The intensity ratio of the lower energy peak to the higher energy peak in EL spectra at 77 K increases with increasing ion dose. The relative intensity of the lower energy peak in the diffused diode with high Zn concentration is weak and the half-widths of peaks are large compared with the implanted diode.

GaAs1-xPx Light Emitting Diodes Produced by Zn Ion Implantation. II. Photoluminescence of p-Type Layers Formed by Ion Implantation and Diffusion

Photoluminescence of Zn implanted and Zn diffused GaAs1-xPx crystals was studied in order to clarify the reason for the extremely high luminescence efficiency of GaAs1-xPx diodes produced by ion implantation compared with diffused diodes. One of the reasons was found to be that the luminescence of the implanted diode occurs over a much wider region of the p-Type layer compared with that of the diffused diode. Moreover, the ion implantation method was found to be capable of producing a p-Type layer without the absorption band below the bandgap due to excess Zn atoms which reduce the luminescence efficiency of the diffused diode. From a photoluminescence study of the p-Type layer with low Zn concentration produced by using ion implantation, one of the main components of the electroluminescence of GaAs1-xPx diodes at low temperatures, which had not clearly been identified, was determined to be a Zn–Te donor-acceptor pair recombination.

Ga(AsP) light-emitting diode formed by ion implantation

Hot ion implantation as a doping technique was used for the fabrication of visible-light-emitting diodes with GaAs1−xPx(x = 0.38 ± 0.01). Zinc ions, p-type dopants, were implanted into n-type (001)-oriented heteroepitaxially grown Ga(AsP)-on-GaAs substrates at 400°C with an energy of 20 keV. Then, thermal treatment at various temperatures was carried out on the sample in order to investigate the effect of annealing on the electrical properties of Zn-implanted layers in the Ga(AsP) substrate. The p-type layer, which was obtained by the ion implantation of 2 × 1015 Zn ions/cm2 with subsequent annealing at 900°C for 40 min, was found to have an effective surface concentration of 1.7 × 1015 carriers/cm2 and a sheet resistivity of about 100 Ω/sq. Red-light-emitting Ga(AsP) diodes fabricated using Zn ion implantation have usually shown an average brightness of 400–600 fL, and sometimes as high as 850 fL at a current density of 10 A/cm2. Diodes, which were formed by means of a standard Zn diffusion technique in an evacuated ampoule at 750°C for 30 min using a ZnAs2 source, had an average brightness of 350–500 fL at the same current density.