Electrical properties of Mg-doped Al_xGa_l-xAs epitaxial layers grown by using molecular beam epitaxy

Magnesium (Mg)-doped Al_x, Ga_l-x As epitaxial layers were grown by using molecular beam epitaxy (MBE) on (100) GaAs substrates under different growth conditions, such as Mg cell temperature, Al mole fraction, substrate temperature and As/Ga beam equivalent pressure (BEP) ratio. The epitaxially-grown Mg-doped Al_xGa_l-xAs layers were characterized using Hall measurements to investigate their electrical properties. The carrier concentration of the Al_0.13Ga_0.87 As layers decreased from 1.86 × 10¹⁷ to 4.87 × 10 ¹⁴ cm^-3 when the substrate temperature was increased. This variance in carrier concentration is attributed to a dramatic decrease in Mg concentration in the III-V epilayers with increasing substrate temperature. The mobility and the carrier concentration of the Mg-doped Al_xGa _l-x As layers also depended on the Al mole fraction and As/Ga BEP ratio. Finally, the Hilsum estimates were found to be in good agreement with the experimental points in the extrapolated curve.