Effects of V/III ratio on ordering in GaInP: Atomic scale mechanisms

Abstract

Ga 0.5 In 0.5 P 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 ͑TBP͒, a newly developed, less-hazardous precursor. For growth on nominally ͑001͒ GaAs substrates misoriented by 3°͑and in some cases by 0°or 6°͒ to produce ͓110͔ 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 ratio͒. For decreasing input partial pressures below 3 Torr for PH 3 and 0.75 Torr for TBP the low-temperature photoluminescence ͑PL͒ 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 ͓110͔-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 ͑2ϫ4͒ reconstructed surface during growth. The difference in the behavior for PH 3 and TBP is interpreted as due to the lower pyrolysis efficiency of PH 3 . The surface structure measured using high-resolution atomic force microscopy indicates that the ͓110͔ 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 PH 3 . 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 ͑2ϫ2͒ reconstruction on the ͑111͒B 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 Ga 0.5 In 0.5 P layers. These high input phosphorus flow rates are found to result in a monotonic increase in the density of ͓110͔-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 ͓110͔ steps at high V/III ratios.

Growth of order/disorder heterostructures in GaInP using a variation in V/III ratio

“…[8][9][10] Thus, in principle, a much more attractive approach would be to change the flow rate of the phosphorus precursor to produce the desired change in order parameter, although the changes in bandgap energy are typically considerably smaller than for changes in temperature. The initial attempts to produce heterostructures in this way used PH 3 as the P precursor at a growth temperature of 620°C.…”

“…6 This has been demonstrated by the recent experimental observation, using surface photo absorption (SPA), that the concentration of 110 [ ] P-dimers on the (001) surface correlates closely with the degree of order (S) produced during OMVPE growth as the growth temperature and partial pressure of the P precursor (P P ) are varied. [7][8][9][10] It has been suggested that the step structure on the surface during growth may also play a role in the ordering process. [10][11][12] (Received March 13, 1997; accepted May 6, 1997)…”

“…[7][8][9][10] It has been suggested that the step structure on the surface during growth may also play a role in the ordering process. [10][11][12] (Received March 13, 1997; accepted May 6, 1997)…”

An atomic ordering based AlInP unicompositional quantum well grown by MOVPE

“…Reduction of the energy bandgap of a CuPt ordered semiconductor alloy depends on its atomic ordering degree, Z. The CuPt atomic ordering degree of a III-V semiconductor epitaxy grown layer has been found changing with the growth conditions, such as the substrate temperature during the growth [7], material growth rate [8], input V/III flux ratio [9] surfactants [10], etc., in the MOVPE growths.…”

Characterization of unicompositional GaInP2 ordering heterostructures grown by variation of V/III ratio

“…The use of variations in V/III ratio to grow heterostructures has a technical advantage over the use of growth temperature despite the fact that the degree of order can currently be controlled over a wider range with variation of growth temperature. [9][10][11] This advantage stems from the fact that changing the growth temperature requires an interruption of the growth for a period of several minutes 6,7 to allow the temperature to stabilize. This interruption could have a negative impact on the quality of the interface in the heterostructure.…”