Mg-doping of GaAs thin films grown by MBE

The influence of the growth conditions in the incorporation of Mg dopant atoms during the growth of GaAs thin films using two different substrate orientations was investigated electrically by Hall effect measurements and by Photoluminescence spectroscopy. Mg-doped GaAs thin films were successfully grown by molecular beam epitaxy with free carrier concentration varying between ~1016 cm-3 to ~1019 cm-3. The wide doping range obtained is suitable to fabricate a great variety of optoelectronic devices. The analysis of the incorporation of Mg atoms for several growth temperatures established two values for the thermal desorption activation energy ED of Mg atoms in the GaAs surface, nominally ED111 = (1.94 ± 0.14) eV for the (111)B samples and ED100 = (1.11 ± 0.16) eV for the (100). Two very close bands were observed in the PL emission of the samples and identified as the electron-Mg acceptor level (e-A) transition, at approximately 1.49 eV, and the donor-to-Mg acceptor level (D-A) transition, at approximately 1.48 eV. At high doping levels a red shift of the e-A and D-A transitions was observed for the (111)B thin films, effect that are related to many-body interactions as the doping level increases.