International Business Machines Corporation

Emilio E Mendez

Leo Esaki

Leroy L Chang

Chin-An Chang

Jerry M Woodall

Tadashi Fukuzawa

Doyeol Ahn

Theoren P Smith, Iii

Hideo Ohno

Ling Y Liu

The present invention is the use of coupled quantum wells in the active region of a semiconductor laser to modulate the frequency and amplitude of the light output of the laser. In a particular embodiment of the present invention the coupled quantum wells are contained in a graded index of refraction semiconductor double heterostructure laser. The active region of this tunable laser consists of two quantum wells having a width of approximately 50 Angstroms or less which are separated by a barrier layer having a width of approximately 20 Angstroms or less. The quantum well material is intrinsic GaAs and the barrier layer is Al.sub.x Ga.sub.1-x As wherein x=0.23. The active region is surrounded by the double heterostructure in which one side is doped p-type and the second side is doped n-type. The resulting laser is a p-i-n type structure. A reverse bias with respect to the flat band voltage of the p-i-n structure is applied across the p-i-n structure which modulates both the frequency and the intensity of the laser output. The tunable laser is pumped with a variety of conventional means, including both electrical and optical pumping. The modulation of the wavelength is approximately linear over a 1.5 volt operating range. A tunable laser, such as the present invention, having an output wavelength modulated by an electric field is useful in the field of optical communications and computing.

Coupled quantum well tunable laser

Resonant tunneling devices having improved peak-to-valley current ratios are disclosed. The resonant tunneling device comprises a quantum well layer surrounded by first and second barrier layers, the first and second barrier layers being comprised of an indirect first III-V compound semiconductor. The first barrier layer being formed on a substrate of a second III-V compound semiconductor having a lattice constant larger than the lattice constant of the first barrier layer thereby inducing a biaxial stress in the first barrier layer. The biaxial stress results in an energy shift at resonance that increases the peak to valley current ratio of the device.

Biaxial-stress barrier shifts in pseudomorphic tunnel devices

The present invention is directed to novel optoelectronic devices, such as light emitters and detectors, that have a unique combination of semiconductor materials that provides a band arrangement resulting in improved efficiency of carrier injection. The devices are quantum well type devices in which discrete electronic states are formed by size quantization effects in the quantum well region. Electromagnetic radiation of emission and absorption occurs by the transition of electrons from a first energy state to a second energy state in either the conduction band or the valence band of the quantum well layer. The bands edges of the layers are offset such that under an appropriate bias, the discrete energy states reside in the bandgap of one of the electrodes and in an allowed region of the other electrode, with one state residing in the conduction band of one electrode and the other state residing in the valence band of the other electrode. The wavelength of the emitted or detected light is inversely proportional to the energy difference between the first and second states. Wavelength customization is facilitated by techniques for adjusting the energy difference.

Optoelectronic devices based on intraband transitions in combinations of

A strained-layer quantum well (QW) or multi-quantum well (MQW) semiconductor laser device (10) having a polarization that is switchable between the TE and the TM modes by an electric field that is externally applied, via an electrode (22) perpendicularly to the layer (16) or layers of the quantum well. The polarization switching is a direct consequence of a valence-band reversal induced by the electric field in the strained-layer quantum well. An inversion population is maintained during the switching process, resulting in rapid switching times.

Polarization-tunable optoelectronic devices

The mobility of carriers in the channel region of a field effect transistor can be increased by providing a layered structure wherein electrons are separated from impurities. The channel is made up of external layers of wide bandgap material and internal layers with a narrower bandgap where the bottom of the conduction band of one layer is below the top of the valence band of the adjacent layer. A structure is shown with a layered channel having AlSb external layers and at least one or both of InAs and GaSb internal layers.

Growing community of inventors

Croton-on-Hudson, NY, United States of America

Emilio E Mendez