Temperature Dependence of Ion Beam Mixing of Ingaas Marker Layers in GaAs
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TEMPERATURE DEPENDENCE OF ION BEAM MIXING OF InGaAs MARKER LAYERS INGaAs D.V.Forbes, J.J. Coleman, J.L.Klatt, and R.S. Averback Materials Research Laboratory and Microelectronics Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL61801. ABSTRACT Ion beam mixing of In0. 20Ga0.80As quantum well marker layers in GaAs following 1MeV Kr ion irradiation has been measured as a function of irradiation temperature and fluence. Secondary Ion Mass Spectrometry (SIMS) was used to measure the diffusion of the In0. 20Gao. 80As layer following irradiation at various temperatures. Rutherford Backscattering (RBS) and channeling methods were used to determine the extent of the amorphization as a result of the implantation. The mixing parameter of the In 0.20Gao. 80As in the GaAs matrix increased from -120 A5/eV at 77K to -160A 5/eV in the temperature range of 300K-450K, but decreased somewhat at 573K. This behavior of Ino.20Gao.80As marker layers will be compared to AlAs marker layers which show similar temperature dependence. These results are interpreted on the basis of thermal spikes and crystal structure. INTRODUCTION Ion beam mixing in metals has been extensively studied and a good understanding of the phenomenon has evolved. 1 Mixing experiments in other classes of materials have not been as systematic or extensive. Part of the difficulty is the lack of the relatively complete knowledge of defect production and defect properties for these materials that exists for metals. In addition, the use of have been helpful in clarifying the irradiation computer simulations, which mechanisms in metals, 2-4 is limited in applicability to semiconductors and insulators owing to the complexity of interatomic forces in these materials. This study was undertaken to investigate the ion beam mixing of an In0 .20Ga 0 .80As marker layer in a GaAs matrix. Use of the marker layer geometry minimizes any chemical driving forces and simplfles analysis. By investigating the ion beam mixing in III-V semiconductor systems, it is hoped to clarify the differences in the mixing mechanisms between metals and semiconductors. The mixing of Ino.20Gao.80As in GaAs exhibits an unusual temperature dependence which is attributed to changes in the crystal structure during irradiation. This5behavior, however, is similar to that observed for AlAs markers in a GaAs matrix. EXPERIMENTAL The sample used in this experiment consists of a thin (-10A) layer of InO. 2 0Gao.80As capped with 800A of GaAs. The samples were grown by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) at 625 C. The irradiations were performed using 1MeV Kr+ at the Van de Graff accelerator facility of the Materials Research Laboratory at the University of Illinois. The ion beam current was kept constant at 50 nA. The background pressure in the irradiation chamber was below 6 x 10-8 Torr. The ion flux was measured to better than 5% using a rotating tungsten wire that intercepted the beam and scattered a fraction of the beam into a surface barrier detector. The Mat. Res.
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