Physics and Applications of Enhanced Quantum Size Effects in (111)-Oriented Quantum Wells

Semiconductor superlattices and quantum wells (QWs) are very important as new man-made materials for novel electronic and photonic devices. These modulated semiconductor structures have been extensively investigated for the past decade; however, they have been prepared almost exclusively on (100)–oriented substrates. The recent progress in molecular beam epitaxy (MBE) has made it possible to grow "device-quality" AlGaAs layers on (111)- and (110)–oriented GaAs substrates.1-3 As a result of comparing several properties of QWs grown on both (111)- and (100)-oriented substrates, we have discovered that a variety of quantum size effects (QSEs) depend upon the quantization direction, that is, the growth axis. In this paper, the experimentally confirmed orientation-dependent QSEs are overviewed, and application to the QW laser is presented.