Chun, Y. S.; Murata, H.; Hsu, T. C.; Ho, I. H.; Su, L. C.; Hosokawa, Y.
Effects of V/III ratio on ordering in GaInP: atomic scale mechanisms
Ga0.5In0.5P layers have been grown by organometallic vapor-phase epitaxy using various values of input V/III ratio for two phosphorus precursors, phosphine, the conventional precursor, and tertiarybutylphosphine (TBP), a newly developed, less-hazardous precursor. For growth on nominally (001) GaAs substrates misoriented by 3° (and in some cases by 0° or 6°) to produce  steps on the surface at a growth temperature of 620 °C, the Cu–Pt-type ordering is found to be strongly affected by the input flow rate of the phosphorus precursor (V/III ratio). For decreasing input partial pressures below 3 Torr for PH3 and 0.75 Torr for TBP the low-temperature photoluminescence (PL) peak energy increases indicating a lower degree of order. This is confirmed by transmission electron diffraction results. The decrease in the degree of order corresponds to a decrease in the concentration of [1-bar 10]-oriented P dimers on the surface, as indicated by surface photoabsorption spectroscopy results. These data indicate that the reduction in ordering is caused by the loss of the (2×4) reconstructed surface during growth. The difference in the behavior for PH3 and TBP is interpreted as due to the lower pyrolysis efficiency of PH3. The surface structure measured using high-resolution atomic force microscopy indicates that the  steps produced by the intentional misorientation of the substrate are bunched to produce supersteps approximately 30–40 Å in height for the lowest V/III ratios. The step height decreases markedly as the input phosphorus partial pressure increases from 0.4 to 0.75 Torr for TBP and from 1 to 3 Torr for PH3. This corresponds to a change from mainly monolayer to predominantly bilayer steps in the vicinal regions between bunched supersteps. Stabilization of the bilayer steps is interpreted as due to formation of the (2×2) reconstruction on the (111)B step edges. The degree of order is an inverted U-shaped function of the flow rate of the phosphorus precursor. Thus, use of very high input V/III ratios is also found to reduce the degree of order in the Ga0.5In0.5P layers. These high input phosphorus flow rates are found to result in a monotonic increase in the density of [1-bar 10]-oriented P dimers on the surface. This decrease in order is believed to be related to a change in the structure of kinks on the  steps at high V/III ratios.
American Institute of Physics (AIP)
Photoabsorption spectroscopy; Transmission electron diffraction; Phosphorus precursor
Epitaxy; Metal organic chemical vapor deposition; Order-disorder in alloys
Chun, Y. S., Murata, H., Hsu, T. C., Ho, I. H., Su, L. C., Hosokawa, Y. & Stringfellow, G. B. (1996). Effects of V/III ratio on ordering in GaInP: atomic scale mechanisms. Journal of Applied Physics, 79(9), 6900.
(c)American Institute of Physics. The following article appeared in Chun, Y. S., Murata, H., Hsu, T. C., Ho, I. H., Su, L. C., Hosokawa, Y. & Stringfellow, G. B., Journal of Applied Physics. 79(9), 1996