GaP

1-x

N

x

alloy is a remarkable and promising semiconductor for its giant band-gap bowing effect and its potential application in optoelectronic devices.In this article

we carried out a series of studies on the optical properties of GaP

1-x

N

x

alloys

especially focusing on the samples with composition x=0.24%

0.6%

0.81%

using temperature-dependent photoluminescence(PL)speetra and transient photoluminescense spectra.At 17 K PL spectra

the GaP

1-x

N

x

alloys exhibit an obvious tendency of band-gap reduction with increasing composition x.When composition x

<

0.24%

the NN

1

zero-phonon line and its replicas in GaP

1-x

N

x

alloys are well resolved

displaying similar characteristic to dilute nitrogen doped GaP;while 0.24%

<

x

<

0.81%

the PL peak energy red-shift effect continues and the emission intensity of the NN

1

replica region is enhanced relative to the corresponding zero-phonon line due to the carriers transferring effect with increasins composition x.In addition

the PL linewidth broadens and the fine structure is gradually illegible.At higher compositions

the PL spectra shift to lower energy and become wide band emission with long emission tail.The fit to the spectra profiles confirm that several new bound states exist below the energy of NN

1

zero-phonon line even when the composition is as low as 0.24%

where the phonon replicas are apparently legible

but the energy of the new bound states might superimpose with the NN

1

phonon replicas.At higher composition(x=0.43%

0.6%)

the new bound states and the carriers transferring effect are more obvious.While at x=0.81%

it is hard to distinguish the energy position of each bound state

indicating a trend from doping bound states to impurity band.Such trend suggests a lower critical point from bound states to impurity band vompared with references.The activation energy of the new bound states decreases with incleasing composition x from 0.24% to 0.6%

but still keeps at a level of the hole binding energy.That suggests the new bound states still have the properties of N-related bound excitons.On the other hand

the double-exponential decay lifetime of the new bound states reveals the different emission mechanism from that of the NN pairs bound excitons.The conclusion is drawn that the new bound states might be the N-related bound states(for instance

the NNN triplets)below the NN

1

bound exciton

or have certain interaction with the NN pairs bound excitons.