ELECTRICAL ACTIVATION OF CARBON DELTA-DOPED (AL,GA)AS GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

Carbon delta-doped (Al,Ga)As was grown by metalorganic vapour-phase ep itaxy using trimethylaluminium (TMAl) or trimethylgallium (TMGa) as a doping precursor. The best C delta-doped Al0.3Ga0.7As has a peak hole density of 1.6 x 10(19) (1.4 x 10(19) for GaAs) cm(-3) with a full hol e profile width at half maximum of 85 Angstrom (84 Angstrom for GaAs). For C delta-doped Al0.3Ga0.7As grown at 630 degrees C, the use of TMG a as a doping precursor leads to both the sheet C atom density and the free hole density increasing with an increase in the total TMGa moles introduced during a delta-doping step. As a result, the electrical ac tivation remains almost constant with the change of TMGa moles supplie d. The sheet C atom density always increases with increasing supply of TMAl, but approaches its maximum value at an amount of TMAl of 6.4 x 10(-7) mol. The electrical activation reduces from > 90% to < 10% when the supply of TMAl increases from 2.1 x 10(-7) to 8 x 10(-7) mol. Reg ardless of the doping precursors, the hole density weakly decreases an d the C atom density significantly increases with increasing growth te mperature. Low growth temperatures are required for high electrical ac tivation. Using optimised growth conditions, C delta-doped pipi doping superlattices with different average hole densities are fabricated to obtain C bulk-doped-like layers.