* Corresponding author. Fax: #49 30 6392 2685; e-mail: knauer@fbh-berlin.de. Journal of Crystal Growth 195 (1998) 694 — 699 Ordering in Ga  In  As  P  grown on GaAs by metalorganic vapour-phase epitaxy A. Knauer*, G. Oelgart, A. Oster, S. Gramlich, F. Bugge, M. Weyers  Ferdinand-Braun-Institut fu ( r Ho ( chstfrequenztechnik, Rudower Chaussee 5, D-12489 Berlin, Germany  Fakulta ( t fu ( r Physik und Geowissenschaften der Universita ( t Leipzig, Linne & str. 5, D-04103 Leipzig, Germany Abstract We have investigated ordering behaviour in MOVPE-grown GaInAsP lattice-matched to GaAs using luminescence and diffraction methods. Our observations indicate that the occurrence of ordering variants depends not only on the growth conditions and the layer composition but is also extremely sensitive to very small substrate misorientation from (0 0 1). For GaInAsP alloys with low arsenic content (y&0.15) the ordering behaviour is very similar to that in the well-studied (In,Ga)P system. Polarization dependent PL reveals that in comparison to InGaP, the degree of ordering in the quaternary gets weaker with rising arsenic content. For higher arsenic content (y*0.5) weak ordering is detected only for layers with y+0.7 when grown with a high V/III ratio in the gas phase. The observed valence-band splittings were + 12 meV for y"0.15 and 8 meV for y"0.7, respectively.  1998 Elsevier Science B.V. All rights reserved. PACS: 78.66.Fd; 78.55.Cr; 61.10.!i; 68.55.!a Keywords: MOVPE; Ordering; InGaAsP; PLE 1. Introduction Quaternary In  Ga  As  P  lattice matched to GaAs (InGaAsP/GaAs) is of considerable contem- porary interest for use in Al-free high-power laser diodes. Ordering is well known for ternary In  Ga  P and GaAs  P  , where CuPt-type or- dering on 111B planes on the group III or V sublattice occurs under certain growth condi- tions [1—3], especially if the ratio of the two column III or V elements is nearly 1. In the quaternary alloys of In  Ga  As  P  grown on GaAs order- ing was observed on the column III sublattice [4,5] and on the group V sublattice [3]. The ordering probability of In  Ga  As  P  grown by meta- lorganic vapour-phase epitaxy (MOVPE) depends on the growth conditions (mainly growth temper- ature, growth rate and ratio of column V to III components in the gas phase R  ) as well as on the layer composition [5,6], doping level and substrate orientation. 0022-0248/98/$ — see front matter  1998 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 9 8 ) 0 0 5 7 6 - 4