Radical generator and molecular beam epitaxy apparatus

A molecular beam epitaxy apparatus comprising:

• a radical generator for generating a radical species, a molecular beam cell for generating a molecular beam or an atomic beam, and a vacuum chamber for accommodating a substrate therein, in use, the substrate being irradiated with the radical species and the molecular beam or the atomic beam in vacuum, to thereby form, on the substrate, a crystal of a compound derived from the element of the radical species and the element of the molecular beam or the atomic beam, the radical generator comprising:
• a supply tube for supplying a gas;
• a plasma-generating tube made of a dielectric material, the plasma-generating tube being connected to the supply tube at the downstream end thereof;
• a coil winding about the outer circumference of the plasma-generating tube, for generating an inductively coupled plasma in the plasma-generating tube;
• and
• an electrode which covers the outer wall of the plasma-generating tube and which is disposed between the coil and the supply tube, for generating a capacitively coupled plasma in the plasma-generating tube and adding the capacitively coupled plasma to the inductively coupled plasma.