The exciton emission spectrum of ZnSe MIS diodes in forward bias electroluminescence has been studied down to the lowest temperatures (20-30K) atwhich it is still possible to pass an appreciable current through a device. Withdiodes prepared on crystals of the highest chemical purity grown by conventional vapour phase techniques

the luminescence consisted almost entirely of the 1LO and 2LO phonon assisted replicas of the

Γ

3

→

Γ

6

free exciton emission.The shapes of the two bands are discussed in terms of the semi-classical theory of Gross et al

[6

7]

with the result that the width asymmetry of the bands are attributed to a Maxwell-Boltzmann distribution of the excitons in an exciton band with an effective exciton temperature close to that of the lattice.