Molecular Beam Epitaxy of Znl−x Cdx Se/ZnSe Heterostructures And Their Optical Properties

Superlattices and quantum wells of Znl−xCdxSe/ZnSe, and heterostructures based on ZnSe/CdSe digital alloys have been grown by molecular beam epitaxy (MBE). Their optical properties were studied with particular emphasis on excitonic absorption and photopumped stimulated emission. Excitonic absorption is easily observable up to 400 K, and is characterized by extremely large absorption coefficients (α ≈ 2×105cm−1). Optically pumped lasing action is obtained at room temperature with a typical threshold intensity of 100 kW/cm2. The lasing mechanism in these II-VI quantum wells appears to be quite different from that in the better studied III-V materials: in our case, the onset of stimulated emission occurs before the saturation of the excitonic absorption, and the stimulated emission occurs at an energy lower than that of the excitonic absorption.