REFLECTANCE-DIFFERENCE DETECTION OF GROWTH OSCILLATIONS

We have observed damped oscillations measured by the reflectance-difference (RD) technique during growth of GaAs by vacuum chemical epitaxy (VCE) using triethylgallium (TEG) and arsine as precursors. The variation in growth rate with incident TEG flux (at 550°C) was found to be linear for growth rates between 0.1 and 0.4 monolayers/s. Our small, compact RD set-up measures, at nearly normal incidence, the difference between the reflectance of light polarized parallel to the [110] direction and parallel to the [110] direction. This gives information on the lower-symmetry surface since the bulk contribution nominally disappears due to the subtraction. Clearly resolved growth oscillations, having an amplitude of up to one fourth of the initial transient, can be obtained during one single time base scan. After arsine stabilization the RD can follow, in real time, the formation of up to 25 single monolayers, each one corresponding to one period of the growth oscillations. Our results prove that RD can be used during continuous growth providing excellent control of the growing GaAs surface. © 1990.