Novel selective area growth of AlGaAs and AlAs with HCl gas by MOVPE

A computational study of gas-phase and surface reactions in deposition and etching of GaAs and AlAs in the presence of HCl

“…The kinetic constant measured by Creighton et al through TPD on a Ga rich surface has a preexponential factor of 10 14 s À1 and an activation energy of 46 kcal/mol [47]. The value reported in Table 11 (reaction S11) is different, since we found that an activation energy of 49 kcal/mol was needed to obtain quantitative agreement with the experimental GaAs growth rate data measured by Shimoyama et al at low temperatures [5]. This 3 kcal/mol increase of the desorption barrier for methyl can be rationalized in terms of a decrease of the sticking coefficient or AsH 3 , a change in the total number of adsorption sites due to the different surface reconstruction, as well as experimental uncertainties.…”

“…Thus, if the growth mechanism (i.e., desorption of methyl controlling at low temperatures) is the same for GaAs and AlAs, the temperature of transition from kinetic to transport controlled regime should be higher for AlAs than from GaAs. However, experimental data indicate the opposite behavior, with the AlAs growth being transport limited while that of GaAs is kinetically controlled [5]. There are at least two possible explanations for this seeming contradiction.…”

“…Two different reactor geometries were considered: the R1 [5] and the R2 [50] reactors. The operating conditions of the R1 and R2 reactors differ in pressure (76 vs.100Torr); Ga(CH 3 ) 3 inlet mole fraction (1.9 Â 10 À4 vs. 2.7 Â 10 À4 ); HCl, when present, inlet mole fraction (1.3 Â 10 À4 vs. 1.8 Â 10 À4 ); and total inlet flow rate (76 vs. 100 slm).…”

“…The experimental conditions in which the experimental data were collected are reported in Refs. [5,10]. Film growth rates were calculated and compared with experimental data using the developed kinetic schemes.…”

“…However, while for GaAs selective deposition can be achieved by controlling the operating conditions such as pressure and temperature, the growth of AlAs is highly nonselective. To improve selectivity, either HCl [3][4][5] or chlorinated precursors (GaCl, AsCl 3 [6,7], DEGaCl and DEAlCl [8,9]) are added to the inlet mixture. The use of HCl allows good control of the Cl/III ratio, which cannot be easily achieved with chlorinated gallium or aluminum precursors.…”