Various epitaxial techniques have been utilized for growing Ga

x

In

1-x

P epilayers on GaAs substrates (GaInP

2

/GaAs). Impurities in the epitaxial GaInP

2

/GaAs seriously effect on its optical and electrical properties. Therefore

it is important to demonstrate what kinds of impurities are common contaminants in epitaxial GaInP

2

/GaAs. A lot of literatures considered C as a contaminant during growing GaInP

2

/GaAs epilayers. Our measurements with CAMECA IMS 4F secondary ion mass spectrometer indicated that there exists contaminant Si instead of C in GaInP

2

/GaAs samples. The shape for the variation of excitation intensity versus peak energy of the photoluminescence (PL) emission nearby 1.17eV in GaInP

2

/GaAs samples illustrated that 1.17eV PL emission could be considered as a donor-acceptor pair (DAP) transition

and furthermore

as a DAP transition of Si

Ga

-V

Ga

where Si

Ga

is a silicon donor on a gallium sublattice site and V

Ga

is a gallium vacancy acceptor.