GaP

1-x

N

x

alloys (or heavily doped nitrogen in GaP) are usually referred as abnormal alloy due to their giant band gap effect. Recently many attentions have been paid to the study on their photoelectric properties. In this paper

the radiative decay and time-resolved spectra were employed to investigate the transient photoluminescence of GaP

1-x

N

x

alloys with

x

=0.05%～3.1% at low temperature. For the low N concentration (

x

=0.05%～0.81%) samples with emission of different NN

i

lines and their sidebands

the (lifetime) is about 30～100 ns in accord with the decay time of NN

4

NN

3

and NN

1

center. For the samples with N concentration up to 1.3%～3.1%

the photoluminescence shows a broaden band and their radiative recombination exhibit the typical exponential decay with 56～36ns

much longer than that of the free excitons (usually about several nanoseconds)

but shorter than that of the samples of GaP

1-x

N

x

with

x

=0.43%～0.81%

whose photoluminescence composed mostly of NN

4

and its sidebands. And it has a trend that

compared to the NN

i

bound excitons

the radiative decay time of the alloys decrease with increasing the N composition. However the lifetime only decrease to the same level of that of the NN

4

center (about 30ns) which indicates that the newly nitrogen impurity band of GaP

1-x

N

x

alloy with x～3% has kept the indirect property of bound excitons with long lifetime

although many PL properties suggested that it has direct band gap. At the same time

due to the longer lifetime for the carriers at the lower energy

the decay time at different detected energies showed that

the higher the detected energy

the shorter the lifetime. In addition to the luminescence decay

the time-resolved photoluminescence were detected. For the high nitrogen concentration samples (GaPN alloys)

the energy peak shifts to the lower energy side with the time delay due to the shorter lifetime at higher energy side. For the low nitrogen concentration samples

especially for

x

=(0.05%) and 0.12%

the relative intensity of deep exciton becomes stronger with the time delay

which is obvious that the energy transfers from shallow center to deep centers e.g. from NN

4

to NN

3

and NN

1

. In previous reports

the energy transfer between different NN

i

excitons was studied by rather indirect method

such as thermal quenching. It is the first time to observe the energy transfer directly between excitons bound to NN

i

.