Electrical characteristics of Mg-doped GaAs epitaxial layers grown by molecular beam epitaxy

The electrical characteristics of magnesium (Mg)-doped GaAs epitaxial layers grown with different substrate temperatures have been investigated by Hall effect and capacitance-voltage (C-V) measurements at room temperature. The carrier concentration obtained by Hall measurements was decreased from 1.4×10¹⁹ to 3.4×10¹⁶ cm^-3 when increasing the substrate temperature in the range 460-540 °C, and thus the maximum attainable doping density was N_A-N_D=1.4×10¹⁹ cm^-3. The depth profiles of doping density, obtained by C-V measurements, show that carriers largely out-diffused toward the surface. This could be attributed to the surface segregation effect, which was predominant in the samples with a high doping density than those with a low doping density. Mg-doped GaAs layers have higher mobility than Be-doped GaAs layers around N_A-N_D=10¹⁸ cm^-3. Thus, it is expected that Mg could be effectively used as p-type dopants for highly doped nanostructured semiconductors.