Recently, there have been a great deal of attention in strained In. Gal-xAs heterostructures grown on the GaAs substrate. This is because the strained systems can provide additional freedom for the material design and various advantages to optoelectronic device applications. For applications to vertical-beam optical devices which are very useful for parallel optical beam processing, however, the advantage offered by the InxGal-xAs material system is crucial. This is because the exciton resonance absorption can occur at energy below the bandgap of the GaAs substrate. This means that there is no need to remove the substrate to transmit the radiation at wavelength of interest. This is in fact the great advantage of the InxGal-xAs material system especially for an integrated-type device. Although recent advancement of the crystal growth techniques enables us to prepare high quality strained epitaxial layers, basic understanding of the band lineup problem is still controversial. Investigations of the pseudomorphic strained heterostructures are therefore important in tailoring the device characteristics.

Recent room temperature observations of lasing, excitonic absorption peaks, and blue LEDs in wide-gap H-VI semi conductor multiple quantum wells (MQWs) provide great promise for unique device applications. A good understanding of the physical mechanisms necessary to account for these recent observations could be extremely important for future device applications. The present CdZnTe/ZnTe system has intriguing properties -alloy quantum wells and strained layers. Nevertheless, excellent sample quality is indicated by a very small Stokes shifts of the photoluminescence (PL) with respect to the PL excitation spectrum (PLE) and narrow absorption linewidths. Furthermore, well-defined room temperature absorption peaks are observed for a wide range of Cd concentrations and well-widths. This offers large flexibility in the choice and composition of materials for better bandgap engineering.

The purpose of Intersubband Transitions in Quantum Wells: Physics and Devices is to facilitate the presentation and discussion of the recent results in theoretical, experimental, and applied aspects of intersubband transitions in quantum wells and dots. This reference work is based on the International Workshop that was held at National Cheng Kung University in Tainan, Taiwan in December 15-18, 1997. Intersubband transitions in quantum wells and quantum dots have attracted considerable attention in recent years, mainly due to the promise of various applications in the mid- and far-infrared regions (2-30 mum). Over 40 invited and contributed papers were presented in this four-day workshop, with topics covering most aspects of the intersubband transition phenomena including: the basic intersubband transition process, multiquantum well infrared photodetector (QWIP) physics, large format (640×480) GaAs QWIP (with 9.0 mum cutoff) focal plane arrays (FPAs) for IR imaging camera applications, infrared modulation, intersubband emission including mid- and long-wavelength quantum cascade (QC) lasers such as short (lambda = 3.4 mum) and long (lambda = 11.5 mum) wavelength room temperature QC lasers, quantum fountain intersubband laser at 15.5 mum wavelength in GaAs/AIGaAs quantum well, harmonic generation and nonlinear effects, ultra-fast phenomena such as terahertz (THz) intersubband emission and detection. Intersubband Transitions in Quantum Wells: Physics and Devices will be of interest to researchers from universities and industrial laboratories working on physics and devices of nanostructures, and researchers in the infrared (IR) community.

Some 30 lectures consider phenomena associated with electrical charges passing through very thin (less than 15 nm) layers of semiconductor material. The optical nonlinearities that result have application in the electronic-devices industry, and provide a real-life example of theoretical one-dimensio"

Semiconductor devices based on lattice mismatched heterostructures have been the subject of much study. This volume focuses on the physics, technology and applications of strained layer quantum wells and superlattices, featuring chapters on aspects ranging from theoretical modeling of quantum-well lasers to materials characterization and assessment by the most prominent researchers in the field. It is an essential reference for both researchers and students of semiconductor lasers, sensors and communications.

Wide-bandgap II-VI compound semiconductor heterostructures are presently being researched for their potential optoelectronic applications at short visible wavelengths, especially in the blue region of the spectrum. In terms of prospective modulator use, a particular difficulty has been the absence so far of the distinct exciton resonances which have been widely exploited e.g. for electro-absorptive purposes in III-V semiconductor quantum wells. In case of ZnSe and related alloys, the problem is fundamental due to the very large exciton-LO phonon coupling: the Frohlich interaction strength for bulk ZnSe is six to eight times larger than that for GaAs.

Experimental and theoretical investigation of electronic states in a strained-layer CdTe/CdZnTe coupled double quantum well structure are presented. The optical properties of this lattice-mismatched heterostructure were characterized with photoluminescence (PL), PL excitation and polarization spectroscopies. Influence of electrical field on exciton states in the strained-layer CdTe/CdZnTe coupled double quantum well structure is experimentally studied. The confined electronic states were calculated in the framework of the envelope function approach, taking into account the strain effect induced by the lattice-mismatch. Experimental results are compared with the calculated transition energies.