Temperature dependence of deep-level photoluminescence in Ga0.5In0.5P epilayers grown by metal-organic chemical vapour deposition

Abstract

The ternary alloy GaxInl_xP grown lattice matched to GaAs has attracted much attention because of its usefulness in optoelectronics and electronic devices. Various epitaxial techniques are utilized to grow high-purity, good-quality materials. The characteristics of these layers have been studied by transmission electron microscopy [1, 2], photoluminescence [3-5], Raman scattering [1, 6], electroreflectance [7] and picosecond absorption dynamics [8]. Deep levels in the epitaxial layers, which could have an important influence on the electrical and optical characteristics of the layers, have received little attention, although the persistent photoconductivity [9] and deep-level transient spectroscopy [10] in Ga0.g9In0.51P layers were reported recently. In this work we studied the near-infrared photoluminescence (NIPL) related to deep levels present in Ga0.sIn0.sP epilayers grown on GaAs substrate by metal-organic chemical vapour deposition (MOCVD) with respect to temperature variations, observed three peaks with energies of 1.17, 0.99 and 0.85 eV, and identified that the 1.17 eV PL emission can be explained well by the recombination of the donor-acceptor pair (DAP), composed of a carbon donor on gallium sublattice site and the next-nearest neighbour gallium vacancy acceptor. Finally, the characteristics of the 1.17 eV emission are discussed using a configuration co-ordinate model. The Ga0.sIn0.sP epilayer, 2/xm thick, used in the experiment was grown on the semi-insulating (1 0 0) GaAs substrate by MOCVD, misoriented 3-5 ° towards one of the (1 1 0) directions at a growth temperature of 700 °C with a group V/III ratio of 30. The lattice mismatch between the Ga0.sIn0.sP layer and GaAs substrate was less than +0.1%. The layer was not intentionally doped. The temperaturedependent NIPL spectra of Ga0.sIn0.5P layer were measured with an ordinary grating monochromator and detected by a liquid-nitrogen-cooled germanium detector using a conventional lock-in technique. Luminescence was excited with the 632.8 nm line of an H e N e laser under proper excitation conditions.