Photodetector-based semiconductor structures with quantum wells
(57) Abstract:Usage: the invention relates to optoelectronics and can be used to create photo-detectors based on epitaxial GaAs/AlxGa1-xAs sensitive to IR-radiation. The essence of the invention: in the photodetector on the basis of semiconductor structures with quantum wells, comprising a substrate of semi-insulating GaAs buffer layer 1 - GaAs first contact layer of N - GaAs, a system of alternating layers of AlxGa1-xAs and GaAs, and in one of the materials system of alternating layers of introduced impurity silicon to the doping level of 21018cm-3and a second contact layer of n - GaAs, silicon is introduced into the layer of AlxGa1-xAs in the form of a monatomic layer, located at a distance not larger Debye length shielded from one boundary of alternating layers. 3 Il. The invention relates to optoelectronics and can be used to create high-performance photodetectors based on epitaxial GaAs/AlxGa1-xAs sensitive to IR-radiation in the Windows of the atmospheric transmittance in the wavelength range =4-14 microns.Known photodetectors that are sensitive to Wed"ptx2">So, for example, photodetectors based ternary compounds CDxHg1-xTe have a maximum sensitivity at =4,5 mm, the photodetectors on the basis of InSb - =3-5 µm .The closest technical solution to the stated photodetector is based on semiconductor structures with quantum wells, comprising a substrate of semi-insulating GaAs buffer layer, an i-GaAs first contact layer of n-GaAs, a system of alternating layers of AlxGa1-xAs and GaAs, and in one of the materials system of alternating layers of introduced impurity silicon to the doping level of 2 1018cm-3and the second contact layer n-GaAs . The mole fraction x of Al in the triple connection is constant and equal to 0.31 in. The doping level of Si in GaAs is 2 to 1018cm-3. Superlattice contains 50 layers each connection (the periodicity of the lattice is equal to 50). Layers of GaAs separated by a wide gap layers of AlxGa1-xAs. E state of n in GaAs localized in the quantum wells. The energy levels of Si in the adjacent GaAs layers do not overlap due to the large thickness of the AlxGa1-xAs. At the border of layers of GaAs and AlxGa1-xAs occurs heterojunctions.A system of alternating layers with a large difference between their thicknesses can be charact out comparable thickness.Known photodetector operates as follows. Radiation with energy = hw equal to the value of the energy gap between the levels En in GaAs and area free conditions, provides the transfer of the first electron in this area, and if you have an external pull field E (causing the slope of the band energy diagram) there is an effect of photoconductivity, the value of G is determined by the expression
G= n l V_ , where n is the concentration of photoexcited electrons; V_ - rate; e is the electron charge.Known photodetector has the following disadvantages.In the state of thermodynamic equilibrium, the electrons are redistributed between the impurity levels in silicon << Si ->> and the level of n in the potential well in GaAs. Thermal excitation of electrons from the level << Si ->> on level n (process II) and their reverse recombination (process III) lead to the fact that the level n is not fully populated. The latter circumstance limits the quantum yield and reduces the effect of photoconductivity, as not all of the electrons are excited quanta hw (process I), in free zone (Fig. 3 is shaded).Another disadvantage of the known photodetector is the presence of dark current (with prajda and reduced dark current.The aim is achieved in that the photodetector on the basis of semiconductor structures with quantum wells, comprising a substrate of semi-insulating GaAs buffer layer, an i-GaAs first contact layer of n-GaAs, a system of alternating layers of AlxGa1-xAs and GaAs, and in one of the materials system of alternating layers of introduced impurity silicon to the doping level of 2 1018cm-3and a second contact layer of n-GaAs, silicon is introduced into the layer of AlxGa1-xAs in the form of a monatomic layer, located at a distance not larger Debye length shielded from one boundary of alternating layers.The invention consists in the following. Implementation in the quantum barrier layer of wide bandgap material layer dopant causes the electrons from the potential well (Si) becomes energetically advantageous to move to level n in the quantum well layer of GaAs. The reverse process because of the significant energy barrier is difficult. This increases the population level1and, accordingly, the quantum yield.Because in the field of localization of electrons no impurity States, the proposed photodetector is characterized by the absence of Ki L Lscreenwhere Lscreen- Debye screening length in AlxGa1-xAs. This helps to ensure a smooth transition of electrons from levels in quantum well quantum hole in the GaAs layer.In Fig. 1 shows schematically the proposed photodetector of Fig. 2, 3 shows the band diagram, respectively, of the inventive photodetector and prototype.The photodetector is a substrate of semi-insulating GaAs 1 on which is formed a buffer layer, an i-GaAs 2, the first contact layer n-GaAs 3, superlattice, consisting of groups 4 alternating layers of doped silicon i-AlxGa1-xAs 5 and undoped i-GaAs 6, and the second contact layer n-GaAs 7.The mole fraction x of Al in the triple connection is selected equal to 0.28.The photodetector grown by molecular-beam epitaxy.In growth chamber molecular beam epitaxy were placed substrate of semi-insulating GaAs. Then on its surface, purified from impurities (C,O2), has formed a buffer layer, an i-GaAs with a thickness of 1 μm. On top of the buffer layer was increased first contact layer of n-GaAs with a thickness of 1 μm. Next formed a superlattice: layer i-AlxGa1-xAs with x=0.28 and the thickness of the layer 300 and the i-GaAs the dopant - silicon with a concentration of 2 to 1018cm-1.The operation was repeated to grow at least 10 groups of layers. On the last layer superlattice formed of the second (upper) contact layer of n-GaAs with a thickness of 200 .The layer thicknesses of the i-GaAs i-AlxGa1-xAs in the superlattice were chosen so that they significantly differed in thickness. This ensures the existence in GaAs quantum wells for electrons and connects the overlap of the wave functions of electrons in adjacent quantum wells.The combination of the molar fraction of x in the triple connection is 0.28, and the thickness of the quantum well GaAs equal to 55 , provides the sensitivity of the photodetector in the range of 8-12 microns.The photodetector operates as follows.In the state of thermodynamic equilibrium electrons with energy levels in the silicon layer in the layer i-AlxGa1-xAs moving to a lower level n layer, an i-GaAs. When the direction of the external radiation with energy h, sufficient to excite the proportion n of these electrons in the free state (continuous continuum of energies), the superlattice creates a conductive state. With application of an external voltage between the first and second contact layers in the sensor occurs, the system is .When this parasitic factor is only the recombination of free electrons in the energy levels of the in-layer and quantum well n. The dark current is weakened, on the one hand, the effect explode quantum wells due to the increase of the barrier, on the other hand, due to the exclusion of hopping conductivity by impurity States between quantum wells.Emergency a few times recombination at the level calls for the constant population of n levels, which ultimately leads to the increase of the quantum yield. The use of the invention will improve detecting ability and the ratio signal/noise photodetectors. PHOTODETECTOR-BASED SEMICONDUCTOR STRUCTURES WITH QUANTUM WELLS, comprising a substrate of semi-insulating GaAs buffer layer, an i - GaAs first contact layer of n - GaAs, a system of alternating layers of AlxGa1-xAs and GaAs, and in one of the materials system of alternating layers of introduced impurity silicon to the doping level of 2 1018cm-3and the second contact layer of n - GaAs, characterized in that the silicon is introduced into the layer of AlxGa1-xAs in the form of a monatomic layer, located at a distance not larger Debye length Ukranian
FIELD: spectral-analytical, pyrometric and thermal-vision equipment.
SUBSTANCE: emitter has electro-luminescent diode of gallium arsenide, generating primary emission in wave length range 0,8-0,9 mcm, and also poly-crystal layer of lead selenide, absorbing primary emission and secondarily emitting in wave length range 2-5 mcm, and lead selenide includes additionally: admixture, directionally changing emission maximum wave length position as well as time of increase and decrease of emission pulse, and admixture, increasing power of emission. Photo-element includes lead selenide layer on dielectric substrate with potential barrier formed therein, and includes admixtures, analogical to those added to lead selenide of emitter. Optron uses emitter and photo-elements. Concentration of addition of cadmium selenide in poly-crystal layer of emitter is 3,5-4,5 times greater, than in photo-element. Open optical channel of Optron is best made with possible filling by gas or liquid, and for optimal synchronization and compactness emitter and/or photo-element can be improved by narrowband optical interference filters.
EFFECT: higher efficiency, broader functional capabilities.
3 cl, 3 tbl, 6 dwg
FIELD: fiber-optic communications, data protection, telecommunications, large-scale integrated circuit diagnosing and testing, single molecule spectrometry, astronomy, and medicine.
SUBSTANCE: proposed device has substrate carrying contact pads, One strip is made of superconductor in the form of meander and its ends are connected to contact pads. Other, additional, semiconductor strip is connected in parallel with above-mentioned strip made in the form of meander. Additional strip is made of superconductor whose kinetic inductance is lower than that of strip made in the form of meander.
EFFECT: enhanced speed, sensitivity, and bandwidth of detector.
9 cl, 2 dwg
FIELD: infrared detectors.
SUBSTANCE: proposed photodiode infrared detector has semiconductor substrate translucent for spectral photodetection region rays and semiconductor graded band-gap structure disposed on substrate;. graded band-gap structure has following layers disposed one on top of other on substrate end. Highly conductive layer of one polarity of conductivity and fixed forbidden gap width produced by heavy doping; layer of other polarity of conductivity and other forbidden gap width in the form of little hump whose value gradually rises from that corresponding to forbidden gap width of preceding layer and then, with smoother decrease to value corresponding to forbidden gap width of preceding layer or smaller. Working layer of same polarity of conductivity as that of preceding layer and fixed forbidden gap width equal to degree of final decrease in forbidden gap width of preceding layer and also equal to forbidden gap width in first of mentioned layer or smaller. Working layer is provided with p-n junction exposed at its surface. Layer disposed on working-layer p-n junction and having gradually increasing forbidden gap width to value corresponding to working layer and polarity of conductivity reverse to that of working layer.
EFFECT: maximized current-power sensitivity, enhanced maximal photodetection frequency, uniform parameters with respect to surface area.
12 cl, 2 dwg
FIELD: power engineering.
SUBSTANCE: invention is used in optical data acquisition systems with high registration efficiency of light radiation by means of avalanche photodiodes with Geiger discharge quenching circuit. Into solid Geiger detector with active restorer, which includes avalanche photodiode the anode whereof is connected to the shift voltage bus and cathode is connected to the first electrode of damping resistor, and a switching restoring transistor, there introduced is the additional damping resistor. The first electrode of the additional damping resistor is connected to the second electrode of damping resistor and to the sink of switching restoring transistor the gate of which is connected to the first electrode of damping resistor, and sink is connected to the second electrode of the additional damping resistor and detector power bus. Switching restoring transistor is made in the form of transistor with a built-in channel.
EFFECT: increasing dynamic range of detector as well as increasing registration efficiency.
FIELD: physics, photography.
SUBSTANCE: invention can be used, for instance in wide-field heat direction finding or thermal imaging devices working in two spectrum regions. The dual spectrum photodetector consists of p modules, each having photosensitive elements, two multiple-element photosensitive lines, a multiplexer and a base. The first multiple-element line is sensitive in one spectrum region and lies on the substrate of the first photosensitive element and the second multiple-element line is sensitive in the other spectrum region and lies on the substrate of the second photosensitive element. In one version first photosensitive elements are trapezium shaped, which enables to arrange the modules such that photosensitive structures, each formed by the lines which are sensitive in one spectrum region, have the shape of regular polygons. In the other version second photosensitive elements are rectangular shaped, which enables arrangement of the modules such that photosensitive structures are in form of a line.
EFFECT: design of dual spectrum large-format multiple-module photosensitive structures of different configurations.
8 cl, 6 dwg
FIELD: physics, semiconductors.
SUBSTANCE: invention relates to microelectronics and can be used in designing semiconductor ultraviolet radiation sensors. A semiconductor UV radiation sensor has a substrate on which there are series-arranged wiring layer made from TiN, a photosensitive AlN layer, and an electrode system which includes a platinum rectifying electrode which is semi-transparent in the C-region of UV radiation, connected to the AlN layer to form a Schottky contact, first and second leads for connecting to an external measuring circuit, where the first lead is connected to the wiring layer and the second to the rectifying electrode. The method of making a semiconductor UV radiation sensor involves successive deposition of a wiring TiN layer and a photosensitive AlN layer onto a substrate through reactive magnetron sputtering on a general processing unit in a nitrogen-containing gas medium with subsequent formation of a platinum rectifying electrode which is semitransparent in the C-region of UV radiation, connected to the photosensitive AlN layer to form a Schottky contact, and leads for connecting the rectifying electrode and the wiring layer to an external measuring circuit. The wiring and photosensitive layers are deposited continuously without allowing cooling down of the substrate. The platinum rectifying electrode is made through three-electrode ion-plasma sputtering of a platinum target at pressure of 0.5-0.6 Pa for 4-6 minutes, target potential of 0.45-0.55 kV and anode current of 0.8+1.2 A. Sensitivity of the end product is equal to 65-72 mA/W.
EFFECT: increased sensitivity of the end product.
2 cl, 2 dwg, 1 tbl
SUBSTANCE: infrared radiation sensitive structure having a substrate whose top layer is made from CdTe, a 10 mcm thick working detector layer made from Hg1-xCdxTe, where x=xd=0.2-0.3, a 0.1-0.2 mcm thick insulating layer made from CdTe, and a top conducting layer with thickness of approximately 0.5 mcm also has a 0.5-6.0 mcm thick lower variband layer between the substrate and the detector layer, where the said variband layer is made from Hg1-xCdxTe, where the value of x gradually falls from a value in the range of 1-(xd+0.1) to a value xd, between the working detector layer and the insulating layer, a top variband layer with thickness of 0.03-1.00 mcm made from Hg1-xCdxTe where the value of x gradually increases from a value xd to a value in the range of 1-(xd+0.1), and dielectric layers between the insulating layer and the top conducting layer. Disclosed also is a method of making the said structure.
EFFECT: possibility of making a highly stable infrared sensitive structure with broad functional capabilities.
12 cl, 1 dwg
SUBSTANCE: method of reducing spectral density of photodiode diffusion current fluctuation in high frequency range involves applying reverse bias V across a p-n junction with a short base and a blocking contact to the base, said reverse bias satisfying the conditions 3kT < q|V| < Vb,t and 3kt < q|V| < Vb,a, where: k is Boltzmann constant; T is temperature; q is electron charge; Vb,t is tunnel breakdown voltage; Vb,a is avalanche breakdown voltage.
EFFECT: disclosed method enables to increase the signal-to-noise ratio of the photodiode in the high frequency range by reducing spectral range of diffusion current fluctuation.
SUBSTANCE: high signal-to-noise (S/N) ratio infrared photodiode has a heavily doped layer (1) of a main p-n junction, a heavily doped layer (2) of an additional p-n junction, a padded base (3) for the main and additional p-n junctions and a substrate (5). The common base (3) has a space-charge region (4) for the main p-n junction. An ohmic contact (6, 7, 8) is formed for each of the layers of the structure. The total thickness of the heavily doped layer of the main p-n junction and the space-charge region of the main p-n junction lying in the common base satisfies a condition defined by a mathematical expression. To increase the S/N ratio in the infrared photodiode, diffusion current of the additional p-n junction and the sum of the diffusion current and photocurrent of the main p-n junction are recorded, and the diffusion current of the additional p-n junction is then used for correlation processing of the signal and noise of the main p-n junction. S/N ratio in the infrared photodiode is increased by using diffusion current of the additional p-n junction, whose noise is correlated with noise of the diffusion current of the main (infrared radiation detecting) p-n junction, for correlation processing of the signal and noise of the main p-n junction.
EFFECT: high signal-to-noise ratio of the infrared photodiode.
2 cl, 2 dwg
SUBSTANCE: inventions can be used in threshold photodetectors for detecting weak electromagnetic radiation in the infrared range. The high signal-to-noise ratio infrared photodiode has a heavily doped layer adjacent to a substrate which is transparent for infrared radiation, whose thickness l1 satisfies the condition: and a weakly doped layer of another conductivity type (base), whose thickness d satisfies the condition d<L. Ohmic contacts are formed along two opposite sides of the periphery of the weakly doped layer. To increase the signal-to-noise ratio in the infrared photodiode, the sum of diffusion current and photocurrent of the p-n junction, and current of the longitudinal conductance of the base, which flows between ohmic contacts formed along two opposite sides of the periphery of the weakly doped layer, is determined, while applying a small voltage across said contacts, which satisfies a given condition.
EFFECT: invention increases the signal-to-noise ratio of the infrared photodiode by using current of longitudinal conductance of the base, whose noise is correlated with noise of the diffusion current of the p-n junction, for correlated processing of the signal and the noise of the p-n junction which detects infrared radiation.
2 cl, 3 dwg