Metalorganic–vapor-phase-epitaxial growth of Mg-doped Ga1−xAlxAs layers and their properties

Magnesium-doped Ga1−xAlxAs layers are grown by metalorganic vapor-phase epitaxy (MOVPE) on (100)-GaAs substrates using bis-cyclopentadienyl magnesium (Cp2Mg) as the organometallic precursor to Mg. Room-temperature hole concentrations in the range of 1×1017–1×1019 cm−3 are achieved with high controllability. The electrical properties are comparable to those for Zn-doped GaAlAs layers. The Mg acceptor energy Ea increases from 25 meV for an Al composition of x=0 to 42 meV for x=0.7. The x dependence of Ea is smaller than that for Zn. Photoluminescence intensities for GaAs and Ga0.7Al0.3As layers are comparable and increased linearly with hole concentration up to the middle of 1018 cm−3. The Mg diffusion coefficients in GaAs and Ga0.7Al0.3As layers are also similar, and are much smaller than the diffusion coefficient for Zn. These results indicate that Mg is a useful p-type dopant in the MOVPE growth of GaAlAs layers.