Gas phase decomposition studies have been combined with metalorganic vapor phase epitaxy (MOVPE) growth and doping experiments to investigate the mechanism behind the Si doping of GaAs grown using tertiarybutylarsine (t-C4H9AsH2 or TBAs) as the Group V source. The use of TBAs leads to an increase in the Si doping efficiency from both SiH4 and Si2H6 sources and this enhancement was proposed to originate from the homogeneous generation of Si-bearing intermediates, (t-C4H9)SiH3 (TBSi) and SiH3AsH2, from reactions between SiH4 and the pyrolysis products of TBAs. We have investigated the formation and role of these intermediates in this Si doping chemistry. Results of our decomposition study show that TBSi pyrolyzes in the gas phase at relatively low temperatures to form SiH4. Consequently, the use of TBSias a Si dopant source results in a Si doping efficiency and temperature dependence that is identical to SiH4. TBSi is therefore not a likely route to increased Si incorporation. Our studies of the co-decomposition of TBAs and SiH4 or Si2H6 show that SiH3AsH2 is a co-pyrolysis product of TBAs and Si2H6, but not of TBAs and SiH4. Furthermore, there is no indication of gas phase interaction between TBAs and SiH4. The results of this study suggest that homogeneous reactions are not as important in this doping chemistry as had previously been considered and that surface processes may instead be responsible for the increase in Si doping observed with TBAs.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Inorganic Chemistry
- Materials Chemistry