Using the methods of X-ray double crystal diffraction and X-ray topography as well as photoluminesccnce (PL)

the influence of mismatch of InGaAsP/InP heterojunction interface lattice on LPE crystal quality was studied. The following results are obtained:1)X-ray double crystal diffraction shows that the halfpeak width of the rocking curve profile of epitaxial layer is five limes larger than that of the substrate when the lattice mismatch perpcndicular to the growth direction (001)(Δa

L

/a

s

) is larger than 3×10

-3

. However

the half-peak width of the rockingcurve piofile of epitaxial layer is the same as that of substrate when (Δa

L

/a

s

) is less than 1.5×10

-4

. A lot of defects and dislocations can be found from (422) surface X-ray reflection topography images in epitaxial layer of sample No.2.On the contrary

a little of defects and dislocations can be found in the sample No.1.2) Photoluminescence spectrum indicates that the band edge PL intensity of sample No.2 is lowei than that of No.l under the same expeiimenlal condition. A possible mechanism is related to the presence of a suiface layer with high recombination velocity. The cause of this high surface recombination velocity possibly leads to a high concentration of nonradiative recombination centers and ladialive recombination deep center. It is found that sample No.2 has a deep center 0.75 eV luminescence band which related to the lattice mismatch.InGaAsP/InP heterojunction interface lattice mismatch is an important factor that has influenced upon epitaxial crystal quality. This kind of lattice mismatch will lead to the inciease of impurity condensation

dislocation and defects as well as radiative recombination deep centeis in LPE processing.