ABSTRACT
R eferences.............................................................................................209
Developments in semiconductor growth technologies, such as metalorganic vapor phase epitaxy [1] and molecular beam epitaxy [2], have enabled fabrication of high-quality lattice-matched and strained quantum well (QW) structures which exhibit many unique material properties that cannot be realized in bulk semiconductors [3]. These properties have resulted in improved photonic devices [3,4] as well as in completely new types of devices [5,6]. For instance, the improvement in laser performance [3], such as lower threshold current density, operation at higher temperatures, modulation at higher frequencies and reduced spectral linewidths [4], is so dramatic that quantum well lasers are now available from a number of commercial sources. QW electroabsorption modulators [7] are possible as a result of the quantum-confined Stark effect (QCSE) [8] which describes the change in the absorption properties of QW structures when an electric field is applied across the structure. The shift in the exciton absorption edge with electric field is observable at room temperature for QW structures but not for bulk semiconductors. The novel self-electro-optic device (SEED) and related devices [5,9], which are proving of importance for large-density optical signal processing and computer applications, are also based on the quantum-confined Stark effect. Very large numbers of extremely small (~ 10 fjim square) devices with low-power consumption can be fabricated permitting the realisation of highly parallel and complex optical architectures. For instance, a 64 x 32 array of symmetric SEED devices, each of which can be operated as a memory element or logic gate has been reported [6].
