PURPOSE: To facilitate excitation of growth material, by using an excitation cell equipment together with a Knudsen cell, while this equipment has a casing which supplies gas to the inside and has an outlet of radicals, and a light source which optically decomposes the gas and supplies light having energy capable of excitation to the inside of the casing.

CONSTITUTION: A first irradiation part 8a for irradiating the inside of an excitation cell equipment 4 with discharge light, and a second irradiation part 8b for irradiating the surface of a substrate B with discharge light are installed at the top part of a discharge tube 8. A light source 5 in the excitation cell equipment 4 is turned on, and ammonia gas is supplied to the inside of the excitation cell equipment 4 via a pipe channel 6 and a gas nozzle 6a, and nitrogen radicals are generated. Light is shed on the subtrate B from the second irradiation part 8b. Since said light has energy larger than that of zinc selenide, the crystal growth of zinc selenide on the substrate B surface is accelerated. Thereby growth material gas or dopant gas can be easily excitated.