A comparative study of carbon incorporation in heavily doped GaAs and Al0.3Ga0.7As grown by solid-source molecular beam epitaxy using carbon tetrabromide

The electrical properties of carbon doped GaAs and AlGaAs were studied as a function of substrate temperature and CBr4 flux for the doping range simil ar to 10(18) - 10(20) cm(-3). Hall measurements indicate a strong reduction in the free carrier concentration of GaAs films grown with the same CBr4 f lux at substrate temperatures above 620 degrees C. Secondary ion mass spect roscopy measurements, however, show no reduction of chemical carbon concent ration. The electrical properties of GaAs:C epilayers grown on (n11)A and B surfaces, where n = 2-5, show strong dependence on crystallographic orient ation. Based on these measurements, the model of free carrier concentration reduction in GaAs:C based on formation of electrically inactive C-C pairs has been proposed. In contrast, no anomalous carbon incorporation in AlGaAs has been detected for the doping range similar to 10(18) - 10(20) cm(-3) a nd the substrate temperature range 550-700 degrees C. The resulting materia l exhibits excellent transport and optical properties. (C) 1999 American Va cuum Society,. [S0734-211X(99)01303-7].