MECHANISM OF DOPING GALLIUM-ARSENIDE WITH CARBON-TETRACHLORIDE DURINGORGANOMETALLIC VAPOR-PHASE EPITAXY

The rates of decomposition of carbon tetrachloride (CCl4), triethylgal lium (TEGa), and tertiarybutylarsine (TBAs), and the rate of GaAs film growth, were measured as a function of the process conditions during organometallic vapor phase epitaxy. In addition, the reaction of CCl4, with the GaAs(001) surface was monitored in ultrahigh vacuum using in frared spectroscopy, temperature-programmed desorption, and scanning t unneling microscopy. These experiments have revealed that CCl4 adsorbs onto Ga sites, and decomposes by transferring chlorine ligands to oth er Ga atoms on the surface. Chlorine and gallium desorb from the surfa ce as GaCl, while the carbon incorporates into the lattice. Triethylga llium is consumed by two competing reactions: GaAs film growth and GaC l etching. Depending on the V/III and IV/III ratios and temperature, t he etch rate can be high enough to prevent any GaAs deposition.