EFFECTS OF SUBSTRATE-TEMPERATURE ON THE PROPERTIES OF IN0.48GA0.52P GROWN BY MOLECULAR-BEAM EPITAXY USING A VALVED PHOSPHORUS CRACKER CELL

We report the molecular-beam epitaxial (MBE) growth of high-quality In 0.48Ga0.52P epitaxial layers on GaAs substrate using a valved phosphor us cracker cell at a wide range of substrate temperature (T-s) from 44 0 to 520 degrees C. Film characterization was carried out using double -axis X-ray diffraction (XRD), low-temperature photoluminescence (PL) and Hall-effect measurement. Typical InGaP layers showed a lattice mis match of <10(-3) and PL full-width at half-maximum (FWHM) as low as 7 meV at 10 K, indicating materials with good structural and optical qua lity. The lattice mismatch remained relatively constant for samples gr own between 440 and 500 degrees C but increased significantly as the s ubstrate temperature was increased to 520 degrees C. Compositional mea surements using XRD showed that indium desorption was significant in s amples grown at substrate temperatures exceeding 500 degrees C. The PL peak energy decreased from 2.014 +/- 0.008 to 1.968 +/- 0.008 eV as t he substrate temperature was increased from 440 to 520 degrees C. The highest PL peak energy of 2.014 +/- 0.008 eV which was indicative of t he highest band gap was measured from the sample grown at T-s = 440 de grees C. The results suggest that highly disordered (i.e. random) InGa P materials can be grown at low substrate temperature with excellent s tructural and optical quality. (C) 1998 Elsevier Science B.V. All righ ts reserved.