ORDERING IN GAINP GROWN AT LOW-TEMPERATURES

Ordering has been studied in GaxIn1-xP with x approximate to 0.52 grown by organometallic vapor phase epitaxy at a rate of 0.5 mu m/h. The GaAs substrates were misoriented from the (001) plane toward the [(1) over bar]00 direction by angles of 0, 3, 6, and 9 degrees. Growth temperature is a key factor in determining both the rate of the ordering process, occurring at the surface during growth, and the annealing process, occurring in the layer after growth. Results are reported for growth at temperatures as low as 520 degrees C. The Cu-Pt type ordering in the epitaxial layers was characterized mainly using photoluminescence (PL) spectroscopy. The PL peak energy decreases as the degree of order increases. For growth at 520 degrees C the layers are not strongly ordered. The lowest 10 K PL peak energy of 1.936 eV, about 60 meV below that of highly disordered Ga0.52In0.48P, occurs for a misorientation angle of 9 degrees. The degree of order, judged from the PL peak energy, generally increases with increasing misorientation angle. The results indicate that the annealing process is slow at 5200C, but so is the ordering process. Nevertheless, the layers are partially ordered and the presence of [110] steps accelerates the surface ordering process.