Kinetics of Te doping in disodering GaInP grown by organometallic vapor phase epitaxy

Te-doped GaInP epitaxial layers were grown by organometallic vapor phase ep itaxy in an effort to clarify the Te disordering mechanism. CuPt ordered Ga InP is produced under normal growth conditions. The addition of Te has been reported to induce disorder. One suggested mechanism for disordering GaInP is the increased step velocity caused by the addition of Te. To test this hypothesis, the effects of growth rate and growth temperature on the disord ering effect of Te were studied. The Te/III ratio in the vapor and the part ial pressure of the P precursor, tertiarybutylphosphine, were kept constant . The behavior of Te incorporation is found to be unusual. The decrease wit h increasing temperature is consistent with Te acting as a volatile impurit y. However, the Te incorporation is also found to be inversely proportional to the growth rate, a characteristic of nonvolatile dopants. A suggested s olution to this apparent contradiction is that the Te, which accumulates at step edges, is not able to keep pace with the steps when they move at the higher velocities. As the growth rate was decreased, with a corresponding d ecrease in measured step velocity, the degree of order was observed to incr ease, in support of this kinetic model. GaInP layers grown at higher temper atures were observed to become much less ordered. Analysis of these data in dicates that the effect is due mainly to the effect of temperature on step velocity. The direct correlation between the step velocity and the degree o f order, as these two growth parameters were varied, confirms that Te disor ders GaInP for kinetic reasons. (C) 2001 American Institute of Physics.