Optical Properties of Compound Semiconductor Heterostructures

Abstract

AbstractDue to the nature of the indirect energy band structure, efficient light emission from silicon is impossible. On the other hand, direct energy band III–V compound semiconductors, such as GaAs, InP, and GaN, are efficient light-emitting materials. By mixing two or three III–V binaries, one can prepare a series ternary or quaternary compounds with added freedoms in the selection of the bandgap energy. Bandgap engineering in heterostructures further allows the creation of new functional devices as will be discussed in Chaps. 9 and 10. Following the discussions of electrical properties of heterojunctions in Chap. 7, we will study their optical properties in this chapter including two major optical processes: the optical absorption and radiative optical transition. The absorption coefficient, spontaneous emission rate, and stimulated emission rate are interrelated through Einstein relations. Finally, the transparency condition of stimulated emission in a semiconductor is discussed.