107 results about "Piezoelectric polarization" patented technology

An object is to improve a positive hole injection efficiency into an active layer in a nitride semiconductor light-emitting device. The nitride semiconductor light-emitting device is formed by stacking nitride semiconductor crystals each of which contains Al and has a polar or semipolar surface either serving as a growth face. The device includes an active layer (103), and first and second composition-graded layers (102, 104). The active layer (103) is interposed between the first and second composition-graded layers (102, 104). Each one of the first and second composition-graded layers is composition-graded so that an Al composition value is rendered smaller as each one of the first and second composition-graded layers (102, 104) comes close to a side where a sum of spontaneous polarization and piezoelectric polarization is negative.

The invention discloses a GaN-based light-emitting diode epitaxial wafer and a manufacturing method of the GaN-based light-emitting diode epitaxial wafer, and belongs to the technical field of semiconductors. The GaN-based light-emitting diode epitaxial wafer comprises a substrate, a buffering layer, an undoped GaN layer, an n-type layer, a multiple-quantum-well layer and a p-type layer, wherein the multiple-quantum-well layer is of a multi-cycle structure, each cycle of the multiple-quantum-well layer comprises an InGaN quantum-well layer and a quantum barrier layer which grows on the InGaN quantum-well layer, each quantum barrier layer comprises a first InGaN layer, an AlGaN layer and a second InGaN layer, and each AlGaN layer and each second InGaN layer grow on each first InGaN layer in sequence. According to the scheme, the first InGaN layer and the second InGaN layer of each quantum barrier layer make contact with each InGaN quantum-well layer, the InGaN quantum-well layers, the first InGaN layers and the second InGaN layers are made of the same materials, the degree of lattice mismatch is low, produced stress is low, the effect of a piezoelectric polarization electric field is poor, the degree of band bending of the InGaN quantum-well layers and the quantum barrier layers becomes lower, the capacity of restraining charge carriers is improved, and when high current is injected, serious leakage current cannot be formed.

A normally-off type field-controlled channel GaN heterojunction diode belongs to the technical field of semiconductor devices. The invention adopts the technology of combining insulating layer-groove, modulation doping and groove-modulation doping to change the conductive channel structure of the existing GaN heterojunction diode, and convert the original normally-on spontaneously polarized GaN heterojunction The junction conductive channel is changed into a normally-off field-controlled conductive channel combining spontaneous polarization and piezoelectric polarization in the present invention, which realizes the field-controlled characteristics of the GaN heterojunction diode conductive channel and reduces the forward conduction resistance and enhanced reverse cut-off capability. The invention has lower forward conduction resistance and power consumption, stronger reverse cut-off ability, and is compatible with AlGaN/GaN HEMT power switching device technology, which is beneficial to the application of the device.

A semiconductor device has a sapphire substrate, a semiconductor layer made of GaN provided on the sapphire substrate, a multilayer film provided on the semiconductor layer, and an electrode in ohmic contact with the multilayer film. The multilayer film has been formed by alternately stacking two types of semiconductor layers having different amounts of piezopolarization or different amounts of spontaneous polarization and each containing an n-type impurity so that electrons are induced at the interface between the two types of semiconductor layers. This allows the contact resistance between the electrode and the multilayer film and a parasitic resistance in a current transmission path to be reduced to values lower than in a conventional semiconductor device.

The invention provides an InGaN-based blue-green light-emitting diode epitaxial growth method and a structure thereof, wherein the growth method of the epitaxial structure comprises specifically the following steps: performing a high temperature annealing process on a sapphire substrate in an ammonia atmosphere, reducing the temperature to 530-580 degrees and adjusting epitaxial growth atmosphere to grow a low temperature InGaN nucleation layer, and then raising the temperature and sequentially growing an InGan unintentionally doped layer, an n-type InGaN layer, an InyGa1-yN/InxGa1-xN(y> x) multi-quantum well active layer, A p-AlInGaN electron blocking layer, A p-type InGaN layer and the p++ type InGaN contact layer. The InGaN-based blue-green LED epitaxial structure provided in the present invention can effectively reduce the piezoelectric polarization field in an active area to thereby improve light emitting efficiency since the structure reduces lattice mismatch between a quantum well material and a matrix material.

The invention discloses a GaN-based light-emitting diode epitaxial wafer and a preparation method thereof, and belongs to the technical field of photoelectron manufacture. The epitaxial wafer comprises a substrate, a buffer layer, a non-doped GaN layer, an N-type contact layer, a stress release layer, an active layer, a P-type electron blocking layer and a P-type contact layer. The stress release layer, comprising a first sublayer, a second sublayer and a third sublayer, is arranged between the N-type contact layer and the active layer, wherein the second sublayer comprises InxGa1-xN layers and N-type doped second GaN layers laminated alternatively, so that the stress formed due to lattice mismatch of a bottom layer can be effectively released, the piezoelectric polarization effect is reduced, and anti-static performance and luminous efficiency of the epitaxial wafer are improved. The first sublayer, the second sublayer and the third sublayer are N-type doped layers, thereby facilitating current expanding, reducing resistance at the two sides of the stress release layer and increasing capacitance at the two sides of the stress release layer; and more electrons are accumulated, so that a better electron blocking effect is achieved, electric leakage channels are reduced, and furthermore, the antistatic capability is further improved.

The invention discloses a terahertz GaN Gunn diode based on an SiC substrate and a manufacturing method thereof, which are used for mainly solving the problems of low output power, poor heat radiation performance and the like in the traditional Gunn device structure. The diode respectively comprises the SiC substrate, an AlN nucleating layer, an n+GaN ohmic contact layer, an electron emitting layer, an n-GaN active layer and an n+GaN ohmic contact layer from bottom to top and is characterized in that the electron emitting layer is made of an InAlN material with 14-22% of an In component and has the thickness of 80-200 nm; a through hole (1) is etched in the SiC substrate; metals Ti/Al/Ni/Au are deposited at the bottom of the substrate; and the metals are connected with an annular electrode (5) through the through hole, so that a longitudinal device structure is formed. The terahertz GaN Gunn diode disclosed by the invention is capable of eliminating a piezoelectric polarization effect and obviously reducing interface dislocation and the length of a Dead Zone, has the advantages of high output power and working frequency, and is applied to working in terahertz frequency bands.

An optical detector has the following strain alloplasm materials on the silicon or sapphire gemstone substrate: with AIN as the buffer layer strain alloplasm structure GAN is grown extendedly. Polarized electric field arisen from the self-piezoelectric polarization effect especially for the strain alloplasm structure can effectively separate optical-electron-cavity couple to lower the direct complex lose to increase the lift of optical-carrier. Alloying metal electrode extends to the inner part of GAN from surface to reduce the surface complex loss of the carrier to raise the collective efficiency.

The invention provides a method for determining the strain of an under-grid barrier layer of a GaN heterojunction field effect transistor, and belongs to the technical field of microelectronics. According to the basic principle of the method, firstly, a semiconductor parameter tester is used for directly obtaining a characteristic curve of capacitance-voltage (C-V) and forward current-voltage (I-V) between a grid electrode and a source electrode of the GaN heterojunction field effect transistor, total under-grid polarization charge density is obtained in combination with barrier layer capacitance analysis, and then the strain of the under-grid barrier layer of the GaN heterojunction field effect transistor is obtained through analysis according to the theories of spontaneous polarization and piezoelectric polarization of GaN heterojunction materials. Compared with existing testing technologies, the testing method is easier, direct and accurate, the resolution ratio is higher, and the problem that an existing testing method cannot test the strain of the under-grid barrier layer is solved.

The invention relates to a preparation method of a low-stress gallium nitride epitaxial layer. The preparation method includes: etching square or round patterns on the front or the back of a substrate; corroding the etched substrate layer with sulfuric acid or sulfuric acid/phosphoric acid mixed solution, cleaning with deionized water, and growing the gallium nitride epitaxial layer on the processed front of the substrate by an MOCVD (metal organic chemical vapor deposition) method; wherein etching depth of the patterns is 1-100 micrometers, and space between each two patterns is 1-10 micrometers. By the preparation method, low stress is borne by the gallium nitride epitaxial layer when the gallium nitride epitaxial layer grows on the processed substrate, production process is simplified, production stability is improved, piezoelectric polarization of active area of a light-emitting diode is avoided, and light-emitting efficiency of the light-emitting diode is improved. The light-emitting efficiency of the light-emitting diode made by the low-stress gallium nitride epitaxial layer is improved by 10%.

A method for enhancement of thermoelectric properties through polarization engineering. Internal electric fields created within a material are used to spatially confine electrons for the purpose of enhancing thermoelectric properties. Electric fields can be induced within a material by the presence of bound charges at interfaces. A combination of spontaneous and piezoelectric polarization can induce this interfacial charge. The fields created by these bound charges have the effect of confining charge carriers near these interfaces. By confining charge carriers to a channel where scattering centers can be deliberately excluded the electron mobility can be enhanced, thus enhancing thermoelectric power factor. Simultaneously, phonons will not be affected by the fields and thus will be subject to the many scattering centers present in the majority of the structure. This allows for simultaneous enhancement of power factor and reduction of thermal conductivity, thus improving the thermoelectric figure of merit, ZT. This approach is also compatible with other strategies for reducing thermal conductivity, for example the inclusion of nanostructures.

The invention relates to a high-temperature testing clamp of a piezoelectric polarization device. The high-temperature testing clamp comprises a supporting base, a lower protecting bush, a heating element, a lower electrode, an upper protecting bush and an upper electrode, wherein the supporting base and the lower protecting bush form an organic whole body; a clamping groove is formed in the supporting base; the heating element is a circular ceramic heating sheet; the circular ceramic heating sheet is mounted in the clamping groove; the lower electrode comprises a copper column with a circular groove in the upper end and a thread rod wiring column; the copper column is mounted on the base and is fitted with the ceramic heating sheet; notches are formed in the two ends of the upper end of the upper protecting bush; the upper protecting bush is mounted above the lower protecting bush; the upper electrode comprises a spring probe and a thread pressing rod; the spring probe is inserted into the thread pressing rod; and the thread pressing rod is mounted on a transverse beam of the upper protecting bush. The testing clamp has a simple structure and low cost; the upper protecting bush and the lower protecting bush are connected in a concave-convex clamping manner and are tightly pressed up and down, so that the fixing effect is good, heat isolation and insulation are good and the utilization is safe; and the spring probe is used as a contact of the upper electrode and can be used for carrying out polarization testing on samples with different radial directions and thicknesses under a high temperature, and the operation is easy.

The invention discloses a manufacturing method of an epitaxial wafer of a GaN-based light emitting diode, and belongs to the technical field of semiconductors. The manufacturing method includes the steps that a substrate is provided; a buffer layer, an undoped GaN layer, an n-type layer, a multi-quantum well layer and a p-type layer are grown on the substrate in sequence, wherein the multiple quantum well layer is of a superlattice structure, each period includes a quantum well layer and a quantum barrier layer, and the growth temperature of at least two quantum barrier layers tightly adjacent to the p-type layer is higher than that of the quantum barrier layers except for the two quantum barrier layers. The growth temperature of the quantum barrier layers close to the n-type layer is low, crystal quality is poor, stress is relieved step by step, then the piezoelectric polarization effect is weakened, and growth of the quantum barrier layers close to the p-type layer is facilitated. As the growth temperature of the quantum barrier layers close to the p-type layer is high, the crystal quality is well improved, the full width at half maximum is decreased, the electron-hole composite probability is further improved, and then the light emitting efficiency of the GaN-based light emitting diode is improved.

In an npn-type HBT, each of an emitter layer and a collector layer is formed of AlGaN and a base layer is formed of GaN. The emitter layer is in contact with a nitrogen polarity surface of the base layer and the collector layer is in contact with a gallium polarity surface of the base layer. An electric charge is generated at each interface due to a spontaneous polarization and a piezo polarization generated in each of the layers. Because of the electric charge, an internal field is generated so as to accelerate electrons in the base layer.

The invention provides an LED (light-emitting diode) epitaxial wafer which comprises a substrate, a gallium nitride nucleating layer, a gallium nitride buffer layer, an N-type gallium nitride layer, a P-type gallium nitride layer, a transparent conducting layer, a P-type electrode, an N-type electrode and an insert layer, wherein the substrate, the gallium nitride nucleating layer, the gallium nitride buffer layer, the N-type gallium nitride layer, the P-type gallium nitride layer, the transparent conducting layer, the P-type electrode and the N-type electrode are sequentially overlaid; the N-type electrode is formed on the etched N-type gallium nitride layer; the insert layer is arranged between the gallium nitride buffer layer and the N-type gallium nitride layer; the insert layer is an AlxGa1-xN layer or an InyAl1-yN layer or is formed in a mode that the AlxGa1-xN layer and the InyAl1-yN layer are overlaid; x is more than 0.1 and less than 1.0; and y is more than 0 and less than 0.25. For the LED epitaxial wafer provided by the invention, high-concentration two-dimension electron gas is generated on a heterogenous interface in the epitaxial wafer under the action of induction of great polarization difference mainly by utilizing the spontaneous polarization and piezoelectric polarization effects of a wurtzite III-Ns material; and due to high electron concentration and high mobility of the two-dimension electron gas, the transverse motion of electrons on the N-type gallium nitride layer can be improved, so that the injection efficiency of a carrier is improved, and thus, the light emitting efficiency of an LED is further improved.

The invention relates to the preparation field of a photoelectric material, particularly to an LED epitaxial wafer. The LED epitaxial wafer comprises a substrate, a gallium nitride layer, an N type gallium nitride layer, an aluminum gallium nitride/gallium nitride multi-quantum-well layer, an electron barrier layer, a P type aluminum gallium nitride layer, a P type contact layer and a P type electrode which are arranged in an overlaying manner in sequence; and the P type aluminum gallium nitride layer is a Mg-doped multilayered polarization-induced Al<x>Ga<1-x>N layer, wherein x is 0.3 to 0.05. The invention aims to solve the technical problems of low luminous efficiency, low internal quantum efficiency and the like caused by electronic leakage and relatively low radiative recombination rate due to spontaneous and piezoelectric polarization in the LED; and the LED epitaxial wafer has the advantages of simple structure, simple and convenient process, convenience in production and suitability for industrial production.

The invention discloses an Si-substrate LED epitaxial wafer and a preparation method therefor, and relates to the technical fields of a device with a special crystal structure and a preparation method for the device. The epitaxial wafer comprises an Si substrate and an epitaxial layer positioned on the surface of the Si substrate; and the epitaxial layer comprises an AlN/AlGaN buffer layer, an non-intentional-doped U-shaped GaN layer, an Si-doped N type GaN layer, an InGaN/Gan multiple-quantum well luminous layer, an electronic battier layer and an Mg-doped P type GaN layer from the bottom up in sequence. According to the epitaxial wafer, the internal quantum efficiency is improved, the piezoelectric polarization electric field is reduced and the wave function alternation of electrons and holes is increased, so that the radiation recombination probability is improved, and the internal quantum efficiency is further improved.

A method of making a semiconductor light-emitting device involves the steps of selecting at least one tilt angle for a primary surface of a substrate to evaluate the direction of piezoelectric polarization in a light-emitting layer, the substrate comprising a group III nitride semiconductor; preparing a substrate having the primary surface, the primary surface having the selected tilt angle, and the primary surface comprising the group III nitride semiconductor; forming a quantum well structure and p- and n-type gallium nitride semiconductor layers for the light-emitting layer at the selected tilt angle to prepare a substrate product; measuring photoluminescence of the substrate product while applying a bias to the substrate product, to determine bias dependence of the photoluminescence; evaluating the direction of the piezoelectric polarization in the light-emitting layer at the selected tilt angle on the primary surface of the substrate by the determined bias dependence; determining which of the primary surface or the back surface of the substrate is to be used, based on the evaluation to select a plane orientation of a growth substrate for making the semiconductor light-emitting device; and forming a semiconductor laminate for the semiconductor light-emitting device on the primary surface of the growth substrate. The tilt angle is defined by the primary surface of the substrate and the (0001) plane of the group III nitride semiconductor. Each of the well layer and the barrier layer of the light-emitting layer extends along a reference plane tilting from a plane perpendicular to a reference axis extending along the c-axis of the group III nitride semiconductor.

The invention discloses a homogeneous epitaxial growth method on a GaN (gallium nitride) substrate. The homogeneous epitaxial growth on the GaN substrate is realized through the lateral epitaxy of an annular pattern mask. The method has the advantages that a perfect GaN epitaxy layer can be obtained, the dislocation density can be effectively reduced, the dislocation density of the epitaxy layer can reach a value lower than 106/cm<2>, the piezoelectric polarization effect of a GaN-based LED (light emitting diode) can be effectively reduced, the inner quantum compounding efficiency and the outer quantum emitting efficiency can be improved, the integral light outlet efficiency can reach more than 1.5 times of that of an ordinary LED, the heating quantity of a device can be effectively reduced, and the service life of the device can be prolonged.

The invention discloses a novel HEMT for improving the piezoelectric polarization intensity. An InGaN layer is inserted below a GaN layer to form the HEMT of an AlxGal-xN/AlN/GaN/InyGal-yN structure on the basis of an HEMT which comprises an AlN isolation layer and is of an AlGaN/AlN/GaN structure. Channels are formed between AlGaN and GaN and between GaN and InGaN respectively and contain 2DEG which is generated through the polarization effect. The InGaN layer is inserted, the lattice constant of GaN in the GaN/InGaN structure is smaller than that of InN, and therefore lattice strain happens to GaN, the intensity of piezoelectric polarization generated by strain is higher than the intensity of piezoelectric polarization between AlGaN and GaN, a device can have a better polarization effect under the same pressure, the density fluctuation of a two-dimensional electron gas face is larger, and sensitivity of the device is improved.

The invention discloses a GaN-based double heterojunction HEMT (High Electron Mobility Transistor) device and a manufacturing method thereof. A structure of the device sequentially comprises a GaN buffer layer, an AlInN barrier layer, a GaN channel layer, an AlGaN isolation layer and an AlGaN barrier layer which are sequentially formed on a sapphire substrate, an AlGaN gate dielectric layer, a source electrode, a grid electrode and a drain electrode formed on the AlGaN gate dielectric layer, an Si3N4 source grid insulation layer formed between the source electrode and the grid electrode, and an Si3N4 drain grid insulation layer formed between the source electrode and the drain electrode. The manufacturing method is characterized by comprising the following steps of adding a layer of AlInN barrier layer between the GaN buffer layer and the GaN channel layer of a conventional GaN HEMT device, utilizing the piezoelectric polarization property of AlInN materials to reduce the current collapse of the device, and forming an AlGaN/GaN/AlInN quantum well structure, so that the binding force on two-dimension electron gas is further improved, and the current collapse is reduced.

The invention provides a luminous device with a superlattice structure active layer, which comprises a substrate and a multilayer III-V group nitride semiconductor structure, wherein the semiconductor structure is formed on the substrate and comprises a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially formed on the substrate, the active layer comprises a superlattice quantum well layer, and the superlattice quantum well layer comprises a potential barrier layer and a superlattice potential well layer. Through the superlattice structure, the crystal defect density of the active layer and the piezoelectric polarization effect generated caused by the lattice dismatching of the active layer can be reduced, the crystal quality and the luminous efficiency of the active layer are improved, and the stability and the reliability of the luminous device are also improved.