Implantation of Rare-Earth Atoms into Si and III-V Compounds

Abstract

Most recent results on doping of Si and semiconductors by the implantation of rare-earth atoms are reviewed. It is shown that up to the concentration of about 10 18 cm' clustering and precipitation can be avoided. Post-implantation annealing leads not only to a decrease in radiation damage, but in some cases also to migration of rare-earth implants. The results of the rare earth lattice location by the Rutherford backscattering measurements are also reported.PACS numbers: 61.80. Jh, Introductory remarksRecently we witness a burst of interest in the doping of Si and III-V compound semiconductors with rare earths (RE). The attention to these exotic dopants was attracted by their potential utilization in constuction of novel light emitting devices (LEDs). Rare earth doped semiconduction are expected to combine the well-known sharp, temperature stable, ultra narrow, atomic-like emission originating from the electronic transitions within the 4f shell of RE impurities with the efficient electrical pumping of this emission by electrons and holes. The inherently long lifetime of the 4f emission limits a possible light output from these devices to small power in a microwatt range. However, if RE doping of Si would result in the constuction of non-degrading efficient LEDs, even with a moderate quantum efficiency at room temperature, then this could lead to a real intrachip (59) 60A. Kozanecki' J.M. Langer' A.R. Peaker optical communication -a long awaited technological goal in the field of VLSI circuits [1,2].Rare earths are very often used as the light emitting centres in wide energy gap ionic crystals and glasses. In fact, most powerful solid state lasers are made of an Nd doped glass. REs are also often utilised in other solid state lasers. In all these cases high dopant concentration is achieved during the crystal or glass growth by adding required amounts of appropriate RE compound to the melt from which a laser rod is pulled out.In semiconductor devices, the active volume is much smaller and planar technologies dominate processing. Very low solubility of REs in covalent semiconduction narrows the range of available technologies of the growth of RE doped semiconduction to non-equilibrium techniques. Among them, two are feasible. One bases on metalloorganic chemical vapour deposition (MOCVD) -a standard technology for semiconductor growth. Initial problem of finding suitable RE compound which would crack in the MOCVD reactor seems to be finally resolved. This technology has been mastered particularly by the group of. K. Takahei [3]. Alternative technology, most suitable for Si doping with REs, is ion implantation, which will be the main topic of our review.Additional problem related to RE doping of Si and III-V compounds is caused by extremely high chemical activity of the RE elements, particularly their notorious affinity to oxygen and other group-VI elements. This can be turned into advantage, however, in the purification of the materials grown from the melt (i.e. liquid phase epitaxy) in the presence of REs [4]...

Lattice sites and damage annealing of Er in low-dose implanted GaAs

“…The radioactive isotope 167 Tm was implanted at 60 keV by means of the ISOLDE facility at CERN, using a 1 mm beam spot, 7° tilted implantation and doses of 6×10 12 Er we used the position-and energy sensitive detection system described in Ref. [16].…”

“…Following high-dose implantation at 250°C (10 15 cm -2 at 150 keV, peak concentration of 2.8×10 20 cm -3 ) and annealing up to 1000°C, Er atoms were found within the <100> but partly outside the <110> atomic rows [11,12]. While such a behaviour could be due to a mixture of substitutional (S) and tetrahedral interstitial (T) Er, it would also be expected for Er within large <100> epitaxial ErAs precipitates.…”

Emission channeling studies of implanted 167mEr in InP

“…Erbium doped InP shows luminescence at a wavelength of 1.54 µm [1][2][3][4][5][6][7][8][9], which is an interesting feature for infrared optoelectronic devices. Incorporation of Er in InP has been reported from both ion implantation [1][2][3][4][5][6][7][8] and doping during growth by metalorganic vapour phase epitaxy (MOVPE) [9].…”

“…Introduction Erbium doped InP shows luminescence at a wavelength of 1.54 µm [1-9], which is an interesting feature for infrared optoelectronic devices. Incorporation of Er in InP has been reported from both ion implantation [1][2][3][4][5][6][7][8] and doping during growth by metalorganic vapour phase epitaxy (MOVPE) [9]. An interesting aspect of the InP:Er system is the fact that its electroluminescence (EL) intensity is thermally stable and only slightly quenched at room temperature.…”

“…Among the various rare earth doped InP systems only the lattice site of implanted Yb has been investigated previously by direct lattice location methods. Using the Rutherford backscattering (RBS) channeling technique, a 50% reduction in the backscattering yield of Yb was observed along the <100> direction [5][6][7][8]. However, the investigation of the axial <100> channeling alone does not allow one to discriminate, for instance, substitutional from tetrahedral interstitial sites or provide sublattice sensitivity and hence is not sufficient to unambiguously derive the lattice location.…”