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We have investigated the impact of organic contaminants from the environment on the electrical characteristics of gate oxides by evaluation of electrical characteristics of metal oxide semiconductor (MOS) capacitors and gas chromatography-mass spectrometry following thermodesorption (TD-GC/MS) analysis of organic species adsorbed on silicon surfaces. It was found that organic contaminants from the environment adsorbed on silicon surfaces deteriorate gate oxide reliability; the increase in both breakdown and infant failure of gate oxides is enhanced by organic contaminants from the environment and depends on gate oxide thickness and the kind of silicon substrate. These results are useful for clarifying the deterioration mechanism of gate oxides caused by organic contaminants on silicon surfaces.

The electrical and optical properties of Si-doped GaAs grown on GaAs (100), (311)A and (311)B substrates by molecular beam epitaxy (MBE) have been studied. A mirror smooth surface is observed for each orientation at low Si atom concentration. Electrical and optical characteristics of the (311)A sample are similar to Si-doped p-type GaAs grown by liquid phase epitaxy, while (311)B samples show almost the same characteristics as (100) samples. Even for a Si atomic concentration up to 1×1020 cm-3, which is too high to keep good surface morphologies of (100) and (311)B samples, excellent morphologies of (311)A samples were obtained. This orientation dependence may be due to different site occupations of Si atoms and surface atom configurations around Si atoms during MBE growth.

We have studied the Si–Be co-doping effect for the suppression of the compositional disordering of AlGaAs–GaAs superlattices (SLs) by SIMS. The Si–Be co-doping is found to suppress the fast Si diffusion which is ascribed to the formation of (SiIII–SiV) pairs. The possible mechanism is that the formation of (BeIII–SiIII) pairs prevents that of (SiIII–SiV) pairs. The suppression of the Si fast diffusion impedes the SL disordering. The threshold concentration of Be required to suppress the SL (300 Å periodicity) disordering is around 2×1018 cm-3 in the case of 1.5×1019 cm-3 Si concentration.

Compositional disordering in Si ion implanted AlGaAs–GaAs superlattices (SL's) has been studied by SIMS. It is found that Si diffuses fast when the Si concentration exceeds 3×1018 cm-3. The disordering of the SL's always occurs with this fast Si diffusion. It is suggested that the disordering of the SL's is induced by the substitutional exchange of (Si I I I –Si V ) pairs with the matrix vacancies. The Si diffusion in the SL layer is not enhanced by the presence of the GaAlAs/GaAs interface.

Disordering in Si implanted GaAs/AlGaAs superlattices is studied by secondary ion mass spectrometry. Samples implanted with 160 keV Si+ at doses 3×1013 to 3×1015 cm-2 are examined before and after 1 h annealing with an SiO2 cap. Dual implantation of 160 keV and 40 keV Si+ is also examined. The results indicate that the disordering of the surface region can be controlled by the concentration balance of implantation-induced defects and Si.

The diffusion profiles of buried Be and Si doped by focused ion beam (FIB) implantation in GaAs after annealing were investigated. The diffusion coefficients of Be and Si were determined by fitting from the results of computer calculations. The diffusion coefficient of FIB-doped Be was enhanced by excess interstitial Be. Beryllium diffusion profiles expand by annealing with a high dose at 850°C. The concentration-dependent diffusion of Si in GaAs doped using a molecular beam was observed. The diffusion coefficient of Si heavily doped by FIB, however, was undetectably small in contrast with that of Be at 850°C.

Compositional disordering in Si implanted GaAs/AlGaAs superlattices has been studied for various implantation energies by secondary ion mass spectrometry. It is found that at higher energy implantation the disordering is suppressed in the surface region and that the disordering in the deeper region becomes incomplete with the implantation energy. These results are well explained by the formation of damage in the surface region and the reduction of Si concentration, respectively.