Typical DAP (donor acceptor pair) recombination behaviours were found for the 1.18eV emission in InP and reported in this paper. The evidences for that the 1.18eV emission band in InP is associated with Mn impurity centers in InP has been published before. No evidence for the DAP nature of this band has been reported previously although DAP recombination as one of possible transition mechanisms was suggested before. The shape line structure of DAP emission has not been reported to be clearly identified in Ⅲ-Ⅴ semiconductor compounds with direct energy gap. In this kind of materials the DAP nature can be established by observing the time-resolved spectra and the intensity-dependent peak shift of the luminescence. The methode of frequency response spectroscopy (FRS) and luminescence decay measurement using boxcar were used in the present work and the emission peaks of this band corresponding long live emission shifting to low energy side as an evidence for the DAP nature was obtained in all the samples measured. The excitation intensity dependent peak shift about 1.8meV was also observed in these samples. The results provides convincing evidence that 1.18eV emission in InP is from DAP recombination. The neutral state of Mn ions in Ⅲ-Ⅴ compounds is Mn

3+

with configuration d4 but the half filled shall configuration d5 is strongly favoured on the ground of energy stability. The ODMR and EPR investigation

which was published previously

also suggested that the transition of 1.18eV band be related to Mn

2+

ion. This implies that the DAP transition of 1.18eV can be expressed as [Mn

2+

]h + D°→[Mn

2+

]+D

+

+ hv

1·18eV

. where D represents inadvertent donors in InP and [Mn

2+

]h means that a hole is loosely bound to half shall state Mn

2+

. [Mn

2+

] h keeps electrically neutral.