Showing papers on "Heterojunction published in 1981"
TL;DR: In this article, it was shown that by modifying the layer structures of the conventional multiquantum well (MQW) lasers, extremely low Jth of 250 A/cm2 (averaged value) for broad-area Fabry-Perot diodes of 200×380 μm was obtained.
Abstract: It is shown that by modifying the layer structures of the conventional multiquantum well (MQW) lasers, extremely low Jth of 250 A/cm2 (averaged value) for broad‐area Fabry–Perot diodes of 200×380 μm was obtained. This was achieved as a result of utilizing the beneficial effects of the two‐dimensional nature of the confined carriers, the improved injection efficiency of the carriers into the GaAs wells, and an increased optical confinement factor in these modified MQW lasers. It was also determined that for low threshold operation the optimal AlAs composition x in the AlxGA1−xAs barrier layers is about 0.19 when GaAs wells are used and for barrier and well thicknesses ≳30 and 100 A, respectively.
238 citations
TL;DR: In this paper, a clear valency electron controllability with substitutional impurity doping in the hydrogenated amorphous silicon carbide has been found, and a new type of a•SiC:H/a•Si:H heterojunction solar cell was developed.
Abstract: A clear valency electron controllability with substitutional impurity doping in the hydrogenated amorphous silicon carbide has been found. The amorphous silicon carbide is produced by the plasma decomposition of [SiH4(1−X)+CH4(X)] with the dopant gas of a B2H6 or PH3 system. Electrical and optical properties of doped amorphous SiC films are briefly demonstrated. Utilizing this a‐SiC:H as a wide‐band‐gap window material, we have developed a new type of a‐SiC:H/a‐Si:H heterojunction solar cell. A typical cell performance is Voc = 0.887 V, Jsc = 12.33 mA/cm2, fill factor = 0.653, and the conversion efficiency of 7.14% under AM‐1 illumination.
227 citations
TL;DR: In this article, a new theory of the electronic properties of heterostructures is proposed, where linear combinations of Bloch waves, both propagating and evanescent, are matched across the interface, leading to simple continuity conditions on the envelope functions, which can be used to solve any heterostructure problem.
Abstract: A new theory of the electronic properties of heterostructures is proposed. Linear combinations of Bloch waves, both propagating and evanescent, are matched across the interface. This leads to simple continuity conditions on the envelope functions, which can be used to solve any heterostructure problem. Calculated optical transitions in GaAs-AlGaAs and InAs-GaSb heterostructures show good agreement with experiment.
191 citations
TL;DR: In this article, the Hall resistance of the two-dimensional electron gas in GaAs•AlxGa1−xAs heterostructures was observed at 4.2 K and at magnetic fields as low as 4.6 T.
Abstract: Quantization of the Hall resistance of the two‐dimensional electron gas in GaAs‐AlxGa1−xAs heterostructures is observed at 4.2 K and at magnetic fields as low as 4.2 T. This demonstrates its practical use as a primary resistance standard.
168 citations
TL;DR: In this paper, a phenomenological model for the electrical conduction in polycrystalline silicon is developed, which combines dopant segregation, carrier trapping, and carrier reflection at grain boundaries.
Abstract: A new phenomenological model for the electrical conduction in polycrystalline silicon is developed. The combined mechanisms of dopant segregation, carrier trapping, and carrier reflection at grain boundaries are proposed to explain the electrical conduction in polycrystalline silicon. The grain boundaries are assumed to behave as an intrinsic wide-band-gap semiconductor forming a heterojunction with the grains. Thermionic emission over the potential barriers created within the grains due to carrier trapping at the grain boundaries and then tunneling through the grain boundaries is proposed as the carrier transport mechanism. A generalized current-voltage relationship is developed which shows that the electrical properties of polycrystalline silicon depend on the properties of the grain boundaries.
142 citations
TL;DR: In this article, the fabrication and device characteristics of experimental back-illuminated InP/InGaAs n-p-n heterojunction phototransistors are described.
Abstract: We describe the fabrication and device characteristics of experimental back-illuminated InP/InGaAs n-p-n heterojunction phototransistors. These devices exhibit photoresponse in the wavelength range of 0.95-1.6 \mu m. An optical gain of 40 at an input power of 1 nW (an improvement of 1000 in sensitivity over previously reported phototransistors) has been observed. Gains as high as 1000 have been achieved for higher incident power levels.
93 citations
TL;DR: In this article, the authors measured the ΔEv for two types of abrupt GaAs-AlAs (110) heterojunctions grown by molecular beam epitaxy: (i) those formed by growth of GaAs on AlAs, and (ii) those grown in the reverse sequence, AlAs on GaAs.
Abstract: We report the direct measurement, by x‐ray photoemission spectroscopy, of the valence‐band discontinuity, ΔEv, for two types of abrupt GaAs–AlAs (110) heterojunctions grown by molecular beam epitaxy: (i) those formed by growth of GaAs on AlAs, and (ii) those grown in the reverse sequence, AlAs on GaAs. The ΔEv at GaAs–AlAs interfaces is, on average, 0.25 eV larger than at AlAs–GaAs interfaces. The ΔEv for GaAs–AlAs heterojunctions was found to average 0.4 eV; the corresponding ΔEv for AlAs–GaAs heterojunctions averaged 0.15 eV. The 0.25 eV difference in average ΔEv value that we observe for the two types of interface demonstrates that the energy‐band discontinuities depend on growth sequence in the GaAs–AlAs heterojunction system.
89 citations
TL;DR: In this paper, a CdO/Cu2O junction formed at room temperature, no copper metal was found at the interface, presumably due to dislocations and impurities in the Cu2O samples as prepared.
87 citations
TL;DR: In this article, the photovoltaic properties of p−Zn3P2/n −ZnO heterojunction solar cells prepared by sputter deposition of ZnO on Zn 3P2 substrates are reported.
Abstract: The photovoltaic properties of p‐Zn3P2/n‐ZnO heterojunction solar cells prepared by sputter deposition of ZnO on Zn3P2 substrates are reported. An active‐area power conversion efficiency of ∼2% has been obtained. The experimental results are discussed on the basis of an interface recombination model. The interface plays a significant role in determining the performance of the device.
87 citations
Patent•
02 Jul 1981
TL;DR: In this article, a p-n-type heterojunction consisting of a first semiconductor layer comprising a photovoltaic active material selected from the class of I-III-VI 2 chalcopyrite ternary materials is vacuum deposited in a thin composition-graded layer.
Abstract: Apparatus for forming thin-film, large area solar cells having a relatively high light-to-electrical energy conversion efficiency and characterized in that the cell comprises a p-n-type heterojunction formed of: (i) a first semiconductor layer comprising a photovoltaic active material selected from the class of I-III-VI 2 chalcopyrite ternary materials which is vacuum deposited in a thin "composition-graded" layer ranging from on the order of about 2.5 microns to about 5.0 microns (≅2.5 μm to ≅5.0 μm) and wherein the lower region of the photovoltaic active material preferably comprises a low resistivity region of p-type semiconductor material having a superimposed region of relatively high resistivity, transient n-type semiconductor material defining a transient p-n homojunction; and (ii), a second semiconductor layer comprising a low resistivity n-type semiconductor material wherein interdiffusion (a) between the elemental constituents of the two discrete juxtaposed regions of the first semiconductor layer defining a transient p-n homojunction layer, and (b) between the transient n-type material in the first semiconductor layer and the second n-type semiconductor layer, causes the transient n-type material in the first semiconductor layer to evolve into p-type material, thereby defining a thin layer heterojunction device characterized by the absence of voids, vacancies and nodules which tend to reduce the energy conversion efficiency of the system.
85 citations
TL;DR: In this article, the effects of the additional selenium on the properties of the films were investigated by structural investigations and photoconductivity measurements, and it was found from the results of the present measurements that compositional changes occur in the films with increasing Selenium/InSe ratio and that single-phase films containing only InSe are obtained at a certain critical ratio.
TL;DR: In this article, the high-energy photpumped laser operation of AlxGa1−xAs−AlAs•AlAs−GaAs quantum-well heterostructures grown by metalorganic chemical vapor deposition (MO‐CVD) is described.
Abstract: The high‐energy (visible‐red) photpumped laser operation (6345 A at 77 K, 6785 A at 300 K) of AlxGa1−xAs‐AlAs‐GaAs quantum‐well heterostructures (QWH) grown by metalorganic chemical vapor deposition (MO‐CVD) is described. The QWH active regions are alloy‐free and consist of GaAs quantum wells and AlAs barrier layers. The effect of the AlAs barrier‐layer thickness on the energy banding of the confined‐carrier states and transitions is demonstrated. The laser operation of the coupled GaAs quantum wells is observed as high as 400–445 meV above the bulk‐GaAs band edge, which agrees with the calculated locations (Lz∼30 A) of the lowest (n = 1) electron, heavy‐hole, and light‐hole confined‐particle states or energy bands.
TL;DR: In this paper, thin-film Cu2S/Cd1−xZnxS heterojunction solar cells with conversion efficiencies of 10% have been prepared on Cd 1−xS with 0.1 ⩽x⩽0.2.
Abstract: Polycrytalline, thin‐film Cu2S/Cd1−xZnxS heterojunction solar cells with conversion efficiencies of 10% have been prepared on Cd1−xZnxS with 0.1⩽x⩽0.2. Light‐generated currents of up to 26 mA/cm2 (prorated to 100 mW/cm2) have been achieved, comparable to the best observed in Cu2S/CdS cells of the same design. The improved performance for Cu2S‐based devices is as a consequence of the higher open‐circuit voltage achieved with the addition of zinc.
TL;DR: In this paper, single-period modulation doped A1xGa1−x As/GaAs heterojunctions have been prepared by molecular beam epitaxy (MBE).
Abstract: Single‐period modulation doped A1xGa1−x As/GaAs heterojunctions have been prepared by molecular beam epitaxy (MBE). Heterojunctions with a Si‐doped A1xGa1−x As layer grown on an unintentionally doped GaAs layer have exhibited enhanced mobility at 78 ° and 300 °K. The A1xGa1−x As, grown with x = 0.25 or x = 0.33, was doped to a level ND?3×1017 cm−3 resulting in a sheet‐charge density of about 8×1011 cm−2. Maximum mobilities of 74 200 cm2/V s at 78 °K and 6930 cm2/V s at 300 °K were observed in different structures. This represents an improvement of more than a factor of 2 over the best previously reported results at 78 °K. These structures, if used for normally off and/or psuedonormally off FET channel layers in high‐speed integrated circuits, can provide improved performance. These extremely high mobilities can lead to a power delay product improvement of about a factor of 2 at room temperature and a factor of more than 12 at liquid‐nitrogen temperature as compared to conventional structures. This increas...
TL;DR: In this paper, various avalanche photodiode structures fabricated in quaternary and ternary alloys are discussed, and the ion implanted GaAlAsSb APD's exhibit a high gain of 100, 82 percent quantum efficiency, and a FWHM of 400 ps.
Abstract: GaAlAsSb quaternary alloys and GaAlSb ternary alloys have been grown by liquid phase epitaxy (LPE) at 550°C and 450°C, respectively. The material compositions and epitaxial structures are suitable for fabricating photodiodes sensitive in the 1.0-1.8 \mu m wavelength range. Various avalanche photodiode structures fabricated in these materials are discussed. The ion implanted GaAlAsSb APD's exhibit a high gain of 100, 82 percent quantum efficiency, and a FWHM of 400 ps. The heterojunction GaAlAsSb APD's have a gain of 40, 92 percent quantum efficiency, and a FWTM of 150 ps. The only remaining material problem which limits the performance of these devices is the high-surface leakage current.
TL;DR: In this paper, a small amount of sulfur to ZnSe results in an improved lattice match with the substrate wafers, where the reduction of the stress at the interface leads to improved photoluminescence properties, as expressed in the narrowing of the width of the nearbandgap peak and in a decrease in the intensity of the self-activated luminescence.
Abstract: Epitaxial layers of ZnSxSe1-x ranging in thickness from 0.1 µm to 4 µm were grown on GaAs and Ge substrates by a low temperature, low pressure organometallic CVD process. The admixture of small amounts of sulfur to ZnSe results in an improved lattice match with the substrate wafers. The exact lattice match occurs at a composition of x = 0.052 for GaAs and x = 0.035 for Ge. The reduction of the stress at the interface leads to improved photoluminescence properties, as expressed in the narrowing of the width of the near-bandgap peak and in a decrease in the intensity of the self-activated luminescence. The performance of n-ZnSe/p-GaAs heterojunctions is also discussed.
TL;DR: In this article, an enhancement mode high electron mobility transistors (E-HEMTs) with selectively doped GaAs/n-AlxGa1-xAs heterojunction structures grown by molecular beam epitaxy are described.
Abstract: Enhancement-mode high electron mobility transistors (E-HEMTs) with selectively doped GaAs/n-AlxGa1-xAs heterojunction structures grown by molecular beam epitaxy are described. E-HEMTs with 2- µm long gates have exhibited the square-law drain characteristic. The device has a gm of 409 mSmm-1 of gate width at 77 K and 193 mSmm-1 at 300 K. This value of gm at 77 K is the highest in all field effect devices reported thus far.
TL;DR: In this paper, current saturation and negative differential resistance are observed as predicted by Monte Carlo simulations for GaAs and AlxGa1−xAs heterojunction layers under hot-electron conditions.
Abstract: Measurements of the current‐voltage characteristics of GaAs‐AlxGa1−xAs heterojunction layers are reported. The experimental results are consistent with the idea of real‐space transfer of the electrons out of the GaAs into the AlxGa1−xAs under hot‐electron conditions. Current saturation and negative differential resistance are observed as predicted by Monte Carlo simulations.
TL;DR: In this paper, a very high optical gain was obtained near the 1.1-µm wavelength by the InGaAsP-InP heterojunction phototransitor.
Abstract: A very high optical gain (~900) was obtained near the 1.1-µm wavelength by the InGaAsP-InP heterojunction phototransitor. The light amplifier, which is an integral device of a heterojunction phototransistor and a double-heterojunction laser (or light-emitting diode with confining layers), is presented. The optical bias method is described for the amplification of a weak incident light.
TL;DR: InP/InGaAsP heterojunction phototransistors with a base terminal have been fabricated, showing hFE, values of up to 2000 as discussed by the authors, which allows us to trade gain for speed by charge extraction from the base.
Abstract: InP/InGaAsP heterojunction phototransistors with a base terminal have been fabricated, showing hFE, values of up to 2000. These devices allow us to trade gain for speed by charge extraction from the base. At a voltage gain of 8 to 9 a response time of 2 ns is observed.
TL;DR: In this paper, the structural properties of double-heterostructures and multiquantum-well structures were investigated by scanning transmission electron microscopy, and the results indicated that the higher quantum efficiency of MQW is correlated with dislocations originating in the substrate.
Abstract: Undoped double‐heterostructures (DH) and multiquantum‐well structures (MQW) grown by molecular beam epitaxy are studied by cathodoluminescence and photoluminescence. Their structural properties are established by scanning transmission electron microscopy. In DH discrete nonradiative centers are observed with densities ∼104–105 cm−2; some of them are correlated with dislocations originating in the substrate. In sharp contrast, MQW show a very uniform luminescence with no nonradiative action at dislocations. These results might explain in part the higher quantum efficiency of MQW grown by molecular beam epitaxy.
TL;DR: Ohmic contacts to n−GaAs using a Ge/GaAs heterojunction have been developed in this article, where free-electron concentrations above 1×1020 cm−3 have been grown on GaAs by molecular beam epitaxy (MBE).
Abstract: Ohmic contacts to n‐GaAs using a Ge/GaAs heterojunction have been developed. Ge layers with free‐electron concentrations above 1×1020 cm−3 have been grown on GaAs by molecular beam epitaxy (MBE). Gold evaporated on such structures forms tunnel contacts through the Ge to the GaAs. The lower barrier height of metals on Ge compared to GaAs and the small barrier at the Ge/GaAs heterojunction facilitates the formation of contacts with specific contact resistances below 10−7 Ω cm2.
Patent•
19 Feb 1981
TL;DR: An amorphous film solar cell of p-i-n heterojunction type, which is produced through the combination of group III-V compound amorphized semiconductor films with a layer of fluorinated or hydrogenated silicon semiconductor material, was proposed in this article.
Abstract: An amorphous film solar cell of p-i-n heterojunction type, which is produced through the combination of group III-V compound amorphous semiconductor films with a layer of fluorinated or hydrogenated amorphous silicon semiconductor material. Selection of the p-i-n layer construction is easier compared to film solar cells of conventional fluorinated or hydrogenated amorphous silicon semiconductor material, efficiency is improved, and there is an increased degree of freedom in choice of the apparatus.
TL;DR: In this article, the growth of Ge on Si substrates by means of a simple chemical vapor deposition (CVD) method is presented, where the epitaxial Ge layers were formed by the decomposition of GeH4 in a H2 ambient at substrate temperatures of 500-900°C.
Abstract: The heteroepitaxial growth of Ge on Si substrates by means of a simple chemical vapor deposition (CVD) method is presented. The epitaxial Ge layers were formed by the decomposition of GeH4 in a H2 ambient at substrate temperatures of 500–900 °C. Smooth surface morphologies and high crystalline quality are obtained in the epitaxial Ge layers. Electrical properties of the Ge films and the resulting p‐Ge/n‐Si heterojunctions were determined. This technique provides a Ge growth method that is compatible with the current CVD processes used in the growth of GaAs.
TL;DR: In this paper, a theoretical study of threshold temperature characteristics of InGaAsP/InP double heterojunction lasers, from the standpoint of carrier leakage from the quaternary active region into the InP confining layers, is presented.
Abstract: This paper presents a theoretical study of threshold temperature characteristics of InGaAsP/InP double heterojunction lasers, from the standpoint of carrier leakage from the quaternary active region into the InP confining layers. The leakage carrier concentration flowing beyond the heterobarrier of the InP confining layer is evaluated through an analysis of heterojunction energy‐band structure. Analytical results indicate that, for an emission wavelength of 1.3 μm, the sharp increase in threshold current near room temperature is caused by carrier leakage. The contribution of carrier leakage is also discussed in relation to various wavelength InGaAsP lasers.
TL;DR: In this paper, a review of the literature on IV-VI film growth by vacuum deposition techniques is briefly reviewed, focusing on the techniques used to deposit pseudobinary alloys with homogeneous composition and the use of foreign impurity dopants.
Patent•
23 Mar 1981TL;DR: In this paper, a majority carrier rectifying barrier semiconductor device housing a planar doped barrier is described. But the device is fabricated in GaAs by an epitaxial growth process, which results in an n+ -i-p+ −i-n+ semiconductor structure wherein an extremely narrow p+ planar Doped region is positioned in adjoining regions of nominally undoped (intrinsic) semiconductive material.
Abstract: Disclosed is a majority carrier rectifying barrier semiconductor device housing a planar doped barrier. The device is fabricated in GaAs by an epitaxial growth process which results in an n+ -i-p+ -i-n+ semiconductor structure wherein an extremely narrow p+ planar doped region is positioned in adjoining regions of nominally undoped (intrinsic) semiconductive material. The narrow widths of the undoped regions and the high densities of the ionized impurities within the space charge region results in rectangular and triangular electric fields and potential barriers, respectively. Independent and continuous control of the barrier height and the asymmetry of the current vs. voltage characteristic is provided through variation of the acceptor charge density and the undoped region widths. Additionally, the capacitance of the device is substantially constant with respect to bias voltage.
TL;DR: In this paper, a two-dimensional electron gas (2 DEG) is accumulated at the interface of GaAs (n)/Al x Ga 1-x As (n) isotype heterojunctions.
Abstract: Previous works have shown that a two-dimensional electron gas (2 DEG) is accumulated at the interface of GaAs (n)/Al x Ga 1-x As (n) isotype heterojunctions. In this paper, a MESFET structure working with this 2 DEG is presented. Theoretical treatments are given, considering that the charge control results from the interpenetration of the Schottky space-charge region and the accumulation layer. A semi-analytical calculation is then developed: conductance, capacitance, source-to-drain current at saturation, and transconductance are predicted for a large-gate FET. Source-to-drain saturation current in short-gate FET is also given. Experimental results obtained in our laboratory and those recently published are compared to calculated data. The good agreement observed in all cases, including low-temperature measurements, clearly shows that the 2 DEG MESFET behavior is actually valid. The high mobility of electrons One can expect from the 2 DEG, particularly at 77 K, suggests that the 2 DEG MESFET is a promising device for microwave and high-speed devices.
TL;DR: In this article, a simple and simple heterostructure interdigital photodetector (HIP) is presented. And the results obtained are comparable to the fastest commercial high speed detectors available today.
Abstract: The demonstration of a novel and simple heterostructure interdigital photodetector (HIP) is reported. The detector displays 50- 60 ps symmetric rise and fall times, low operating voltages (∼10-25V), with a dc responsivity greater than 0.3 A/W at λ = 0.83 µm. The results obtained are comparable to the fastest commercial high speed detectors available today. The device is compatible with planar technology and thus should lend itself to integration with MESFET's or other microwave integrated circuits. Lastly, the concept of using a heterostructure to confine the injected carriers should ultimately provide high speed operation by limiting the detrimental effects of carrier diffusion and traps in the semi-insulating substrate.
TL;DR: In this article, hot electron effects were observed at a field as low as 10 V/cm, which is the first report of hot electron phenomena in GaAs at such small fields.
Abstract: Multiple-period (Al, Ga)As/GaAs modulation doped heterojunction structures have been grown with molecular beam epitaxy Electron mobilities of about 200 000 cm2/Vs at 10 K and 90000 cm2/Vs at 77 K with associated sheet carrier concentrations of about 2×1012 cm−2 have been observed The current parallel to the interfaces for low electric fields was examined as a function of lattice temperature The electron mobility has been observed to be strongly dependent on the strength of the electric field, and hot electron effects were observable at a field as low as 10 V/cm To our knowledge this is the first report of hot electron phenomena in GaAs at such small fields