VERY HIGH-CARBON DELTA-DOPING CONCENTRATION IN ALXGA1-XAS GROWN BY METALORGANIC VAPOR-PHASE EPITAXY USING TRIMETHYLALUMINUM AS A DOPING PRECURSOR

Using trimethylaluminum (TMAI) or trimethylgallium (TMGa) as a doping precursor, carbon delta-doped AlxGa1-xAs has been grown in metalorgani c vapor phase epitaxy. Compared to TMGa, TMAI exhibits very high carbo n delta-doping efficiency. The best hole profile of carbon delta-doped Al0.3Ga0.7As grown at 580 degrees C using TMAI as a doping precursor has a peak hole density of 1.6x10(19) cm(-3) for a full width at half- maximum of 85 Angstrom with most of the incorporated carbon atoms bein g electrically active. When TMGa is used as the doping precursor, the hole density of carbon delta-doped AlxGa1-xAs significantly increases with an increase of the Al mole fraction. By comparison, the use of TM AI almost induces independence of the hole density on the Al mole frac tion. The hole density of carbon delta-doped Al0.3Ga0.7As weakly incre ases when reducing the delta-doping temperature regardless of the dopi ng precursors. The hole density of carbon delta-doped Al0.3Ga0.7As gro wn at 580 degrees C is proportionally associated with the moles of TMG a or TMAI totally input during a delta-doping step. Using heavily carb on delta-doped layers in Al0.3Ga0.7As, a carbon delta-doped pipi dopin g superlattice possessing a bulk-doped-like hole profile with an avera ge hole density of 1.1x10(19) -3 is therefore demonstrated as an alter native with unique advantages over other cm conventional carbon bulk-d oping approaches. (C) 1996 American Institute of Physics.