HEAVY CARBON DOPING IN LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY OF GAAS USING TRIMETHYLARSENIC - A COMPARISON BETWEEN THE CARRIER GASES N-2 AND H-2

The carbon doping behavior of trimethylarsenic (TMAs) in low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) of GaAs was studied in the temperature range of 550 to 700 degrees C and at various trimethylarsenic/trimethylgallium (TMAs/TMGa) ratios using the carrier gas N-2 in comparison to the standard H-2. At a growth temperature as high as 600 degrees C, perfectly specular layers with a hole concentration equaling the carbon concentration of 1.7 x 10(20) cm(-3) and a mobility of 55 cm(2)/V.s were achieved for the carrier gas nitrogen. This is the highest fully active carbon concentration ever reported for MOVPE material, to our knowledge, and more than double the hole concentration obtained for the carrier hydrogen under the same growth conditions. This result indicates that the carrier N-2 is better suited for heavy carbon doping with TMAs at such a high growth temperature as 600 degrees C than the carrier H-2, and is therefore more compatible to growth requirements for (AlGa)As/GaAs heterostructures than H-2. A method is introduced with which the accepters are activated without post-growth anneal.