MOLECULAR-BEAM EPITAXIAL-GROWTH OF CARBON-DOPED GAAS WITH ELEMENTAL GALLIUM AND ARSENIC SOURCES AND A CCL4 GAS-SOURCE

CCl4 has been used as a carbon acceptor dopant source for GaAs grown by elemental source molecular beam epitaxy. Deposition of CCl4 during normal arsenic stabilized growth of GaAs resulted in low mobility, p-type material. Attempts to thermally crack the CCl4 using a heated gas cracking source resulted in an even lower hole concentration and mobility. One possible explanation for this ineffective acceptor doping behavior, relative to growth environments containing hydrogen (metalorganic chemical vapor deposition) where CCl4 is an effective dopant, is that hydrogen plays a role in the incorporation of the carbon. Another possible explanation for the poor doping behavior is that the CCl4 was being modified by the gas cracker, even at relatively low gas cracker temperatures. Further experimentation with different injection schemes will be necessary to better understand the doping behavior. Depositing the CCl4 onto static, gallium-rich surfaces produces GaAs:C with hole mobilities comparable to GaAs:Be. Average hole concentrations as high as 4 x 10(19) have been demonstrated. Carbon doped AlGaAs/GaAs heterojunction bipolor transistors (HBTs) have been fabricated with the same characteristics as Be doped HBTs grown in the same MBE system.