An optical study of the properties of (AlxGa1-x)(0.5)In0.49P epitaxial layers with varying composition, hydrostatic pressure and GaAs substrate orientation

Optical studies were performed using photoluminescence (PL) at 300 and 4.2 K, and photoluminescence excitation spectroscopy (PLE) at 4.2 K, to evaluat e the optical properties of (AlxGa1 - x)(0.51)In0.49P, grown on (001) GaAs misorientated 10 degrees towards < 111 > A substrate type, as a function of x, the Al male-fraction in the solid, from x=0 to 0.46. An estimate of the room temperature band-gap dependence on x was determined from PL and PLE t o be Ep = 1.9 + 0.7x eV. The 300 K PL intensity was measured as a function of x for the above samples and two other substrate orientations which were also included in each growth run. A factor of similar to 25 decrease in PL intensity was observed for samples grown on 10 and 15 degrees misorientated substrates as the emission wavelength changed from similar to 650 (x=0) to 570 nm (x=0.46). In comparison, material grown on the 2 degrees misorienta ted substrate showed a much larger decrease in PL intensity of similar to 1 20 over the same compositional range. The PL emission energy of the materia l grown on the 2 degrees misorientation substrates was similar to 40 meV lo wer than the PL emission energy of the material grown on the 10 and 15 degr ees misorientated substrates. This shift of similar to 40 meV is consistent over the whole compositional range studied and is explained by differences in the degree of ordering of the AlGalnP alloy as a function of substrate orientation. Hydrostatic pressure measurements have revealed that the varia tion of PL efficiency with Al compositions can be explained by a combinatio n of the increasing concentration of non-radiative centres associated with increasing Al in (AlxGa1 -x)(0.51)In0.49P (extrinsic effects) and the decre asing T-X separation energy in these materials (intrinsic effects). (C) 199 9 Elsevier Science S.A. All rights reserved.