PURPOSE: To remove temperature fluctuation in a molecular beam cell caused by opening/closing of a shutter, to improve quality of growing crystal, by installing the shutter at the front of a jetting port in the molecular beam source cell so that heat rays projecting from the molecular beam source never return to the source again.
CONSTITUTION: A shutter 15 is shaped in a horn bending downward and has an opening part at its pointed end. Such a shape enables heat radiant light to reflect inside the shutter and attain to the pointed end of the horn and to be released from the opening at the pointed end, without reflecting on a molecular beam source 33 and bouncing. Even in a state in which the molecular beam source cell is covered with the shutter 15, the heat radiant light does not reflect on the molecular beam source 33. And, in an open state in which the shutter is excepted, the heat radiant light does not reflect and therefore heating temperature of the molecular beam source 33 is made constant regardless of shutter's opening/closing. Therefore, high quality of growth crystal can be realized with constitutional rate of growing crystal and fluctuation in film thickness to be decreased.