Be diffusion during post-growth annealing has been studied in InGaAs epitaxial layers, grown between two undoped InGaAs layers. To explain the observed concentration profiles and related diffusion mechanisms, a general substitutional–interstitial model is proposed. On the one hand, a simultaneous diffusion by dissociative and kick-out models is suggested and, on the other hand, the Fermi-level effect is used to explain the functional dependence change of the effective diffusion coefficient of beryllium species with its concentration. The concentration dependent diffusivity has also been covered to perform an improved data fitting of Be diffusion profiles.

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A mass spectrometric analysis of the neutral products and the positive ions extracted from discharges in C2F6 and CHF 3, sustained at 25 kHz with pressures between 0.2 and 0.8 torr (1 torr = 133 Pa) was performed. The apparatus calibration and the calculation of the partial pressures from mass spectra at 70 eV are described The formation reactions of the many detected products : CF4, C2F 2, C2F4, C3F6, C3F 8, C4F8, C2HF5 and HF are discussed. Variations in the neutral composition of these plasmas, induced by etching of SiO2 and Si were observed These variations are explained by the consumption of CFn radicals (n = 1 to 3) at the etched surface. The main positive ions produced are CF+ 3, CF+, CF+2 and CHF+ 2. Their formation is explained by the ionization of neutral molecules and molecular radicals

To explain the observed beryllium diffusion profiles in the InGaAs base layer of InGaAs/InP heterojunction bipolar transistors, the most basic form of Frank - Turnbull mechanism is proposed and implemented in a computer simulation program. A double profile is obtained which may be explained by the reduction in the vacancy concentration in the bulk of the crystal below its equilibrium concentration. Calculated profiles are computed and compared with our experimental profiles and with other beryllium diffusion profiles available in InGaAs. Some parameters such as diffusion time, diffusion coefficients, concentrations and vacancy bulk generation are investigated. The effect of V/III ratio on post-growth annealing profiles is also simulated. The point defect concentration in epitaxial layers during beryllium diffusion in InGaAs is discussed.

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