Dual implants of C+ and Ga+ ions in GaAs have been investigated by sheet-resistivity and Hall-effect measurements. Efficient doping has been achieved by dual implantation, even at an annealing temperature of 700 °C. Analysis of electrical profiles indicates that the concentration of substitutional atoms in As sites is less than the implanted dose; the remaining C atoms are believed to out-diffuse through encapsulation during annealing. Although the doping efficiency for the dual implants is higher than that of the single implants, the effective compensation ratio is about the same, which suggests that ’’self-compensation’’ may be the predominant mechanism in the implanted samples.
The electroreflectance (ER) technique for measuring ion implantation damage is developed and evaluated. The technique is useful for measuring damage profiles in GaAs samples. The ER measurement using the E1 critical point is shown to be primarily sensitive to a depth of 0.008 μm. The damage profiles of S-, Cd-, Be-, and Ne-implanted GaAs samples are determined employing a selective etch technique. The annealing characteristics of these GaAs implants are shown to be dose dependent.
A previously presented technique of measuring radiation damage using electroreflectance (ER) measurement is used to detect disorder dependencies for light and heavy ions as a function of flux and fluence. Lighter-mass ions (Ne, N, and O) cause increasing damage with increasing flux for fluences less than 5×1013 cm−2 because of the decrease in radiation-enhanced annealing. At higher fluences, the damage decreases with increasing flux probably because of thermal annealing. Heavy ions (Cd, Te, and Xe) exhibit the same type of behavior but at lower fluences because of the smaller penetration depths. The ER measurements of damage in ion-implanted GaAs show clearly that the radiation-enhanced and thermal-annealing processes depend upon the energy density and damage concentration in the crystal.
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