Ion-beam synthesis of GaN in silicon

Abstract

Abstract. The structure and composition of a subsurface silicon layer subjected to a dual implantation of Ga and N ions with subsequent annealing have been investigated using X-ray photoelectron spectroscopy, electron spin resonance, X-ray diffraction, Raman microscopy, transmission electron microscopy. The results indicate a possibility of ion-beam synthesis of GaN composite nanostructures in silicon-based materials. IntroductionNew development stage of electronic technologies is characterized by the transfer from conventional microelectronics to optoelectronics and integrated optics. This requires synthesis of light emitters and photodetectors on a single chip for different ranges of wavelengths, including the ultra-violet range. A key material of conventional microelectronics -silicon -cannot be used as an efficient light source because of its indirect band gap. This fact has stimulated the search for other light-emitting materials compatible with silicon technology. Such a compatibility would allow the usage of tremendous longterm achievements of silicon technology and could give high economic effect. For example, the cost of a silicon wafer is seven times lower than that of a GaAs wafer of the same area.It is known that LEDs, lasers and photodetectors on the basis of III-nitrides, in particular gallium nitride, have excellent performance as well as high resistance to radiation, chemically aggressive environment and temperature. However, there is a problem of high cost of GaN and difficulties of its integration into a silicon or other low-cost substrates. Fabrication of high-quality epitaxial III-nitride layers on silicon is difficult due to the high lattice mismatch and differences in thermal expansion coefficients of the materials [1]. It results in a high dislocation density (more than 1·10 6 cm -2 ) and the degradation of device performance.One of the perspective solutions to this problem is the ion-beam synthesis of III-V (especially GaN) nanocrystals by dual (sequential) ion implantation into silicon or into dielectric films (SiO 2 , Si 3 N 4 , Al 2 O 3 , HfO 2 , etc.) deposited on silicon substrate. An advantage of ion implantation over the other synthesis methods (like epitaxy) is in a high controllability of the implanted layer composition and concentration of implanted atoms (not restricted by the thermodynamic solubility limit), an ability of local phase synthesis with focused implantation, and perfect compatibility of this method with the existing CMOS-technology. Using ion implantation with subsequent annealing permit to synthesize not only continuous layers, but semiconductor nanocrystals in different matrices, including amorphous matrices.