30 results about "Quantum-confined Stark effect" patented technology

A device contains at least one wavelength-tunable multilayer interference reflector controlled by an applied voltage and at least one cavity. The stopband edge wavelength of the wavelength-tunable multilayer interference reflector is preferably electrooptically tuned using the quantum confined Stark effect in the vicinity of the cavity mode (or a composite cavity mode), resulting in a modulated transmittance of the multilayer interference reflector. A light-emitting medium is preferably introduced in the cavity or in one of the cavities permitting the optoelectronic device to work as an intensity-modulated light-emitting diode or diode laser by applying an injection current. The device preferably contains at least three electric contacts to apply forward or reverse bias and may operate as a vertical cavity surface emitting light-emitter or modulator or as an edge-emitting light emitter or modulator. Using a multilayer interference reflector containing tunable section allows also obtaining a wavelength-tunable laser or a wavelength-tunable resonant cavity photodetector in the case where the optical field profile in the active cavity or cavities is affected by the stopband wavelength shift. Adding additional modulator sections enables applications in semiconductor optical amplifiers, frequency converters or lock-in optical amplifiers.

The invention discloses a multilayer LED chip structure and a preparation method thereof. The structure comprises a sapphire substrate, a GaN buffer layer formed on the sapphire substrate through low temperature epitaxial growth, a n-type GaN formed on the GaN buffer layer through high temperature epitaxial growth, an AlGaN layer formed on the n-type GaN through high temperature epitaxial growth, an InGaN/GaN quantum well relaxation layer growing on the AlGaN layer for three periods, an InGaN/GaN quantum well active area growing on the InGaN/GaN quantum well relaxation layer for seven periods, a p-type AlGaN electronic blocking layer growing on the InGaN/GaN quantum well active area, a p-type GaN layer growing on the electronic blocking layer and a heavily-doped p-type GaN contact layer growing on the p-type GaN layer. The structure can effectively reduce the dislocation density of a material in an epitaxial layer, reduces the influence of quantum-confined Stark effect, and improves the internal quantum efficiency of an LED.

The invention provides an epitaxial structure for improving luminous efficiency. The epitaxial structure for improving the luminous efficiency sequentially comprises a substrate, a first GaN (Gallium Nitride) buffer layer, a second GaN buffer layer, an N-type GaN layer, a multi-quantum well (MQW) structure, a light-emitting layer multi-quantum well structure, a p-type GaN layer, a p-type AlGaN (aluminium gallium nitride) layer, a p-type GaN layer and a p-type contact layer from the bottom up, wherein the multi-quantum well structure consists of n layers of InxGa1-XN/GaN multi-quantum wells; the widths, the depths and the barrier heights of the n layers of the multi-quantum wells increase layer by layer; the barrier widths of the n layers of the multi-quantum wells decrease layer by layer; the well widths increasing layer by layer and the barrier widths decreasing layer by layer form regular correspondence; and n is an integer in a range of 2-12. A preparation method of the epitaxial structure for improving the luminous efficiency can optimize concentration distribution of electrons, reduce stresses generated in growth processes of multi-quantum wells, reduce a quantum confined stark effect (QCSE) and improve the luminous efficiency of the multi-quantum wells.

An optical transmitter implemented with two QPSK (Quadrature Phase Shift Keying) modulators is disclosed. Each of the QPSK modulators provides a waveguide made of semiconductor material inducing the QCSE (Quantum Confined Stark Effect) by a bias supplied thereto. The optical performance of one of the QPSK modulators is determined by supplying a deep bias to the other of the QPSK modulator to eliminate the optical output therefrom.

Semiconductor electrooptic medium shows behavior different from a medium based on quantum confined Stark Effect. A preferred embodiment has a type-II heterojunction, selected such, that, in zero electric field, an electron and a hole are localized on the opposite sides of the heterojunction having a negligible or very small overlap of the wave functions, and correspondingly, a zero or a very small exciton oscillator strength. Applying an electric field results in squeezing of the wave functions to the heterojunction which strongly increases the overlap of the electron and the hole wave functions, resulting in a strong increase of the exciton oscillator strength. Another embodiment of the novel electrooptic medium includes a heterojunction between a layer and a superlattice, wherein an electron and a hole in the zero electric field are localized on the opposite sides of the heterojunction, the latter being effectively a type-II heterojunction. Yet another embodiment has a heterojunction between two superlattices, wherein an electron and a hole in a zero electric field are localized on the opposite sides of the heterojunction, the latter operating effectively as a type-II heterojunction. A further embodiment has an ultrathin quantum well layer confined by barrier layers, having an essentially different barrier heights and a thick layer, wherein, in a zero electric field, a charged particle of one sign having a large effective mass is localized in this ultrathin layer, and a particle having a different sign of the charge, having a small effective mass is not localized in this ultrathin layer, but is localized mainly in the neighboring thick layer. Thus, the heterojunction between the two layers operates effectively as a type-II heterojunction. Applying an electric field to all types of the electrooptic medium of the present invention results in a dramatic increase of the exciton oscillator strength and, therefore, in a large positive refractive index change at the photon energies below the exciton absorption peak. A very strong increase in the optical transition photon energy can be achieved, when necessary.

The invention provides a new quantum well structure, which can further effectively increase the recombination probability of carrier, improve quantum efficiency and realize optimization and improvement of efficiency of a photoelectric device. AlInGaN is used as a barrier, an In and Al component gradual barrier layer structure is designed to substitute barrier layer structure design of the conventional quantum well structure. The In component is doped into the barrier layer structure of the quantum well, the band bending of the quantum well is reduced, a quantum confined stark effect is weakened, the electron blocking efficiency of an electron barrier layer is improved, a hole injection efficiency of the quantum well is increased, spatial wave function overlap of electrons and space is increased, and these have a positive effect on improvement of luminous efficiency of an LED (Light Emitting Diode); meanwhile the Al component is doped into the barrier layer structure of the quantum well, so migration of the electrons to a P layer is effectively blocked; through the gradual component design of the AlInGaN, the influence of a polarization electric field can be reduced, and the spontaneous emission spectrum strength of the quantum well is improved.

The invention provides a non-polar surface quantum dot light-emitting diode, which comprises a substrate, a u-type GaN layer, an n-type GaN layer, an active region, a p-type electron blocking layer and a p-type GaN layer, wherein the u-type GaN layer, the n-type GaN layer, the active region, the p-type electron blocking layer and the p-type GaN layer are laminated on the substrate in sequence and are in non-polar surface; and the active region comprises an InGaN quantum dot potential well layer and a GaN barrier layer in periodic distribution and in non-polar surface. The invention also provides a preparation method of the non-polar surface quantum dot light-emitting diode. By laminating the non-polar surface epitaxial structures on the substrate in sequence, influence of a quantum-confined stark effect on internal quantum efficiency of the device can be eliminated, and a polarization effect can be eliminated effectively; and besides, light wavelength of the light-emitting diode in such crystal orientation can extend to deep green or even orange light area, so that the problem of "green gap" in existing compound semiconductor light-emitting devices can be solved.

A nanostructure fabricated on a semiconductor light-emitting device induces strain in the active region. The active device includes at least one quantum heterostructure, in which the strain changes the extent of Quantum Confined Stark Effect, and thus modifies the wavelength of light emission. By mixing strain relaxation and strain induction effects there is a spectral broadening of the light emission, providing polychromatic light emission.

A nanostructure fabricated on a semiconductor light-emitting device induces strain in the active region. The active device includes at least one quantum heterostructure, in which the strain changes the extent of Quantum Confined Stark Effect, and thus modifies the wavelength of light emission. By mixing strain relaxation and strain induction effects there is a spectral broadening of the light emission, providing polychromatic light emission.

The invention discloses a GaN-based light-emitting diode which comprises a substrate, a buffer layer, an N-type layer, a multiple quantum well active layer and a P-type layer, wherein the multiple quantum well active layer consists of InGaN quantum wells and InAlN quantum barriers. In the GaN-based light-emitting diode, InAlN materials in lattice matching with InGaN quantum well materials serve as the quantum barriers, so that a QCSE (Quantum-Confined Stark Effect) is improved, Efficiency Droop of a device is improved, the light-emitting efficiency of the device is improved, and IQE (Internal Quantum Efficiency) of an LED (Light-Emitting Diode) assembly is improved.

The invention provides an InGaN quantum dot LED epitaxial structure with a strain reduction structure, which comprises a sapphire substrate layer, a GaN low-temperature nucleation layer, a U-GaN layer, an N-GaN layer, a first InGaN strain reduction layer, an InGaN quantum dot active region, an electron blocking layer and a P-GaN layer, wherein the first InGaN strain reduction layer is an InGaN monolayer or InGaN/GaN superlattice whose In component is lower than 10%. The InGaNInGaN strain reduction layer is introduced in the InGaN quantum dot LED epitaxial structure. The InGaN quantum dot LED epitaxial structure with the strain reduction structure in the invention brings about the following effects: (1) weakening the quantum-confined stark effect; (2) reducing the defect density of the InGaN quantum dot active region; (3) making up for the shortcomings of insufficient quantum dot density.

The invention belongs to the technical field of a semiconductor and discloses a nano-column ultraviolet LED and a preparation method and application thereof. The preparation method is characterized byarranging a layer of nano-silicon dioxide particles on the surface of an ultraviolet LED epitaxial wafer; and then, with the nano-silicon dioxide particles being a mask, carrying out etching on the ultraviolet LED epitaxial wafer to form a nano-column structure, and obtaining a nano-column ultraviolet LED. The nano-column ultraviolet LED comprises a substrate, a pre-paved Al layer, a AlN layer, aAlGaN layer, a u-GaN layer, an n-GaN layer, quantum well nano-columns and p-GaN nano-columns from the bottom up in sequence. The nano-column ultraviolet LED helps to release the stress of an LED quantum well, reduces the quantum-confined stark effect and enhances LED device performance; and besides, the preparation method is simple and feasible, omitting complex steps and cost in preparing the mask, and can adjust the size of the nano-columns through SiO2 in different particle sizes.

A thick gallium nitride (GaN) film is formed on a LiAlO₂ substrate through two stages. First, GaN nanorods are formed on the LiAlO₂ substrate through chemical vapor deposition (CVD). Then the thick GaN film is formed through hydride vapor phase epitaxy (HVPE) by using the GaN nanorods as nucleus sites. In this way, a quantum confined stark effect (QCSE) becomes small and a problem of spreading lithium element into gaps in GaN on using the LiAlO₂ substrate is mended.

The invention provides a electroabsorption modulator. The modulator comprises an SOI waveguide; an active region, the active region comprising amultiple quantum well (MQW) region; and a coupler for coupling the SOI waveguide to the active region. The coupler comprising: a transit waveguide coupling region;a buffer waveguide coupling region; and a taper region; wherein, the transit waveguide coupling region couples light between the SOI waveguide and the buffer waveguide coupling region; and the buffer waveguide coupling region couples light between the transit waveguide region and the active region via the taper region.

A lithium aluminum oxide (LiAlO₂) substrate suitable for a zinc oxide (ZnO) buffer layer is found. The ZnO buffer layer is grown on the LiAlO₂ substrate. Because the LiAlO₂ substrate has a similar structure to that of the ZnO buffer layer, a quantum confined stark effect (QCSE) is effectively eliminated. And a photoelectrical device made with the present invention, like a light emitting diode, a piezoelectric material or a laser diode, thus obtains an enhanced light emitting efficiency.