Micro Raman scattering was employed at room temperature to investigate the properties of GaInP

2

alloys grown by MOVPE.The excitation wavelength is 5145nm.The geometry is back-scattering.GaInP

2

has CuPt-like ordered structure along [111] which results in special optical properties such as the reduction of band gap

the doubling of PL peak

the temperature and excitation intensity dependence of photoluminescence

the splitting of valence-band

etc.The Raman spectra show two-mode behavior.In addition to the GaP-like LO

1

mode(ordered samples at 383cm

-1

disordered sample at 381cm

-1

) and the InP-like LO

2

mode around 360cm

-1

the InP-like TO

2

mode around 330cm

-1

and the GaP like TO

1

mode hidden in LO

2

are observed.To alloy with zinc-blende structure

the TO mode is forbidden with back-scattering geometry under Raman selection rule.But to the CuPt like ordered structure

the TO mode becomes Raman active by the reason of symmetry reduction from

T

d

to C

3v

.At the Raman shift about 200cm

-1

all the samples have the same disorder-activated longitudinal acoustic bands(DALA).Besides the DALA

the ordered samples exhibit folded longitudinal acoustic mode (FLA) around 205cm

-1

.This mode belongs to the

L

point folded to the Γ point as a result of the doubling of the unit cell of Brillouin zone.The intensity of the FLA peak is believed to be stronger with increasing the degree of order.In addition to the LO

1

+LO

2

mode

the splitting of LO

2

into LO

2

and LO

2

in ordered samples induced by superlattice effect resulting from the atom ordering is detected.In the ordered Raman spectra

from which the disordered's is subtracted

one can tell the FLA peak and the LO

2

more clearly.In addition

there is another peak around 375cm

-1

which is probably the LO

1

splitting from LO

1

.By analyzing the PL peak energy and the

b

/

a

ratio of the valley between GaP like and InP-like LO to the height of InP-like LO

2

it exhibits that the value of b/a ratio reduces with the increase of ordering.On one hand

it is because that the forbidden TO becomes Raman active.On the other hand

it is probably due to the consequence of the splitting of LO

1

into LO

1

and LO

1

and LO

2

into LO

2

and LO

2

.Besides the value of b/a ratio which represents the degree of order:the smaller the value of b/a

the greater the ordering degree

the high intensity of FLA mode also corresponds to high degree of order.