Light-Emitting Devices and Semiconductor Lasers

Direct-gap semiconductors are the basic materials of many light-emitting devices (LEDs) and laser-diodes (LDs) found in our daily life. We give here some fundamental physical properties of these materials and how they are implemented in such devices. We start with a description of the emitted spectrum of LEDs using a generalized Kirchhoff law and introduce emitter characteristics like efficiency and efficacy. In particular, the properties of various ternary and quaternary semiconductor alloys are discussed with focus on the achievable tunability of the emission wavelength. Also energy quantization in colloidal quantum dots and its application in full-color displays is illustrated. We then turn to the realization and optimization of optical gain and lasing in LDs. Finally the electron relaxation dynamics in quantum cascade lasers is described.