Abstract: A method of selective light detection uses an optical multi-stable device selectively exhibiting a variety of optical multi-stable characteristics for incident light wavelengths or intensities. The device includes an optically serial connection of two optical bistable elements. Each of the optical bistable elements includes a photodiode having a light absorbing layer including a quantum well structure. The photodiodes are reverse biased by respective voltage sources through respective series resistors so that an optical bistable characteristic for incident light wavelength or intensity is achieved for each photodiode. The characteristic of the second photodiode includes four stable photocurrents at respective wavelengths.

Abstract: The output electromagnetic power of optoelectric heterojunction semiconductor devices having an active semiconductor layer with a mobile charge-carrier plasma is controlled by applying a microwave electric field inside the active layer by means of at least two semiconductor contacts to the active layer that are conducting to at least one type of mobile charge carrier and blocking to another type of charge carrier. An electrical signal is applied inside the active layer to transform the distribution of energies and equivalent temperature of the charge carriers of the mobile charge-carrier plasma in order to control light emission and absorption in the active layer. A heterojunction semiconductor laser is disclosed with two sets of electrical contacts: one to apply pumping currents and the other to control the electric field.

Abstract: A resonant-tunneling transistor comprises a first semiconductor layer acting as a collector, a second semiconductor layer provided on the first semiconductor layer and forming a potential barrier of electrons in the conduction band, a third semiconductor layer provided on the second semiconductor layer and forming a quantum well of electrons in the conduction band, a fourth semiconductor layer provided on the third semiconductor layer and forming a quantum well of holes in the valence band, the fourth semiconductor layer simultaneously forming a potential barrier of electrons in the conduction band, a fifth semiconductor layer provided on the fourth semiconductor layer acting as an emitter, a first electrode provided in contact with the first semiconductor layer for recovering electrons therefrom, a second electrode provided in contact with the fifth semiconductor layer for injecting electrons thereinto, and an optical passage for introducing an optical beam to the first semiconductor layer.

Abstract: A semiconductor radio-frequency power detector comprises, in a stack, an ohmic contact layer, undoped layer of a first semiconductor material, such as GaAs, of thickness l.sub.1, an undoped layer of a second semiconductor material, such as AlGaAs, of larger band gap than the first semiconductor material, the thickness of the layer being such that transport in the layer is primarily by intraband tunnelling, a second undoped layer of the first semiconductor material of thickness l.sub.2, where l.sub.2 >20l.sub.1, and a second ohmic contact layer. The difference between the thicknesses of the layers of the first semiconductor material gives rise to asymmetry in the current density/applied voltage characteristic for the device. An n+ layer may be incorporated in the second layer of the intrinsic first material to reduce "band bending" and to increase the current density.

Abstract: A novel concept and structure of a semiconductor circuit are disclosed which utilize the fact that the interaction between the carriers such as electrons and holes supplied in a meso-scopic region and the potential field formed in the meso-scopic region leads to such effects as quantum interference and resonance, with the result that the output intensity is changed.

Abstract: A non-linear semiconductor optical device comprises a first quantum well layer having discrete quantum levels of carriers including a first quantum level for electrons and a second quantum level for holes with an energy gap corresponding to a wavelength of an incident optical beam; a pair of barrier layers provided above and below the first quantum well layer in contact therewith with a thickness that allows a tunneling of the carriers therethrough for defining a potential well in correspondence to the first quantum well layer; and a second quantum well layer provided in contact with the barrier layers for accepting the carriers that have been created in the first quantum well layer upon excitation by the incident optical beam and escaped therefrom by tunneling through the barrier layer. The second quantum well layer comprises a material that has a conduction band including therein a .GAMMA. valley and an X valley, wherein said .GAMMA.

Abstract: Long wavelength infrared detection is achieved by a detector made with layers of quantum well material bounded on each side by barrier material to form paired quantum wells, each quantum well having a single energy level. The width and depth of the paired quantum wells, and the spacing therebetween, are selected to split the single energy level with an upper energy level near the top of the energy wells. The spacing is selected for splitting the single energy level into two energy levels with a difference between levels sufficiently small for detection of infrared radiation of a desired wavelength.

Abstract: An enhanced mobility semiconductor comprising a host quantum well having at least two charge carrier barrier layers of a wide bandgap material, each of the two charge carrier barrier layers being separated by a conducting region containing charge carriers is provided. A number of phonon barriers having a predetermined thickness are formed in the conducting region wherein the predetermined thickness is chosen to allow charge carrier tunneling through the phonon barriers.