Surface photoabsorption study of the effect of substrate misorientation on ordering in GaInP

Substrate orientation strongly affects Cu-Pt ordering in Ga0.5In0.5P layers grown by organometallic vapor phase epitaxy. In situ surface photoabsorption SPA measurements were used to measure the concentration of 1 10-oriented P dimers, characteristic of the 2 4 reconstructed surface, as a function of substrate misorientation from 001. For substrates misoriented toward either 110 or 111 A or 1 10 or 111 B, the P-dimer concentration is found to decrease systematically as the misorientation angle increases from 0° to 15.8° at 620 °C with tertiarybutylphosphine TBP partial pressures of 10, 50, and 200 Pa. The P-dimer concentrations on substrates misoriented toward 110 are higher than for those misoriented toward 1 10. The Ga0.5In0.5P layers were found to form the Cu-Pt structure during growth. The degree of order, determined from 20 K photoluminescence measurements, shows a strong correlation with the concentration of 1 10-oriented P dimers. The data also clearly show the effect of step structure on Cu-Pt ordering. They indicate that 110 steps formed by misorientation toward 1 10 enhance ordering while 1 10 steps formed by misorientation toward 110 retard ordering.