Optical Studies of Strained Pseudomorphic Semiconductor Heterostructures UnderExternal Pressure

摘要

Epilayers and quantum well heterostructures of group III-V and II-VI binary andternary compounds offer an exciting array of band gaps and physical properties. The band gaps range from the infrared to the near ultraviolet region (0-1 to 3 eV); continuous tuning of the band gap is achieved by means of alloying of alloying strain and quantum confinement. Pseudomorphic heterostructures with large lattice mismatch and minimal dislocation and defects at the interface have been successfully grown by various techniques. This paper reviews the effects of strain on the optical and electronic properties, determination of strain, tuning of strain, and the structural stability of these metastable structures. Photoreflectance photoluminescence and Raman scattering studies as a function of temperature and externally-applied hydrostatic pressure are discussed. Owing to the different compressibilities and thermal expansion coefficients of the constituent members of a heterostructure the strain can be continuously tuned by these perturbations. Depending on the relative signs of the lattice mismatch strain and the pressure (or temperature) induced strain, the net strain in the structure could increase or decrease. Examples of both cases are presented. jg.