Showing papers on "Heterojunction published in 1976"
TL;DR: In this paper, the fabrication procedures and characteristics of several thin-film p−CuInSe2/n−CdS heterojunction solar cells are presented, and two modes of operation (illumination through CdS or through InSe2) are discussed, under 100 mW/cm2 tungsten-halogen illumination for 1.2
Abstract: The fabrication procedures and characteristics of several thin‐film p‐CuInSe2/n‐CdS heterojunction solar cells are presented. Two modes of operation (illumination through CuInSe2 or through CdS) are discussed. Efficiencies in the range of 4–5% are reported, under 100 mW/cm2 tungsten‐halogen illumination for 1.2‐cm2 devices. Included are the spectral response and J‐V characteristics for these photovoltaic junctions.
248 citations
TL;DR: In this article, the conduction band edge discontinuity ΔEc = 0.56 eV at n−CdS/p−InP junctions is reported, and the performance of this discontinuity and others are compared with photoemission data and with Van Vechten's extension of these data to many tetrahedrally coordinated semiconductors.
Abstract: The discontinuity ΔEc=0.56 eV in the conduction band edge at n‐CdS/p‐InP junctions is reported. This discontinuity and others are compared with photoemission data and with Van Vechten’s extension of these data to many tetrahedrally coordinated semiconductors. Agreement between measured discontinuities and theoretical predictions is very good. Predictions are made for band parameters pertinent to interfaces involving AIIBIVCV2 compounds with zinc blende, chalcopyrite, or wurtzite crystal structures.
208 citations
PARC1
TL;DR: In this paper, a general formulation for arbitrary-shaped gratings which need not be small in size was developed for radiated power from traveling waves as a function of grating tooth height, tooth width, refractive index, waveguide thickness, and period.
Abstract: Grating-coupled radiation in GaAs:GaAlAs lasers and waveguides is analyzed. A general formulation is developed for arbitrary-shaped gratings which need not be small in size. Two methods are used to solve the resulting equations in the case of rectangular-shaped gratings. The first is a perturbation technique and the second is iterative in nature. The iterative procedure converges to a numerical exact solution in many cases of practical interest and indicates that the perturbation results are quite accurate. Curves are presented for radiated power from traveling waves as a function of grating tooth height, tooth width, refractive index, waveguide thickness, and period for rectangular gratings in heterostructure waveguiding geometries. It is shown that radiation is not a monotonically increasing function of tooth height, but rather maxima occur when the teeth are half the optical wavelength in the material. Also, in particular geometries with an air:GaAs grating interface, radiated power of a mode can exceed 100 cm-1.
176 citations
TL;DR: In this article, the indium tin oxide films sputtered on to p-silicon using ion-beam techniques and showed significant photovoltaic effects when exposed to sunlight.
Abstract: Heterojunction diodes of indium tin oxide films sputtered on to p-silicon using ion-beam techniques display significant photovoltaic effects when exposed to sunlight. Galvanomagnetic and optical measurements confirm that the oxide films are highly degenerate transparent semiconductors. At a tin oxide concentration of 10%, an open-circuit voltage of 0.51 V was observed along with a short-circuit current of 32 mA/sq cm, a fill factor of 0.70, and a conversion efficiency of 12%. As the concentration was raised to 70%, the voltage remained steady, the current fell to 27 mA/sq cm, and the fill factor fell to 0.60
148 citations
TL;DR: In this paper, the lattice parameter and band gap of ZnxCd1−xS films were found to change almost linearly with composition and electrical resistivity increases from <1 to ≳1010Ω cm as x increases from 0 to 1.
Abstract: ZnxCd1−xS films suitable for use in solar cells have been formed by simultaneous evaporating of ZnS and CdS. Lattice parameter and band gap are found to change almost linearly with composition. Electrical resistivity increases from <1 to ≳1010Ω cm as x increases from 0 to 1. Nonseries‐resistance‐limited ZnxCd1−xS‐CuyS photovoltaic cells have exhibited open‐circuit voltages greater than 0.7 V, apparently due to a better match between the ZnxCd1−xS and CuyS electron affinities.
114 citations
TL;DR: In this paper, a determination of the effective interfacial recombination at Al0.25Ga0.75As/GaAs and Al 0.5As/GAAs heterojunctions was made based on the dependence of the minority-carrier lifetime on junction spacing.
Abstract: A determination has been made of the effective interfacial recombination at Al0.25Ga0.75As/GaAs and Al0.5Ga0.5As/GaAs heterojunctions. The recombination velocity was deduced from the dependence of the minority‐carrier lifetime on junction spacing in heterojunction diodes. For heterojunction spacings in excess of about 1 μm, the interfacial recombination can be characterized by a recombination velocity of 4×103 and 8×103 cm/s for Al0.25Ga0.75As/GaAs and Al0.5Ga0.5As/GaAs heterojunctions, respectively. However, for double‐heterojunction spacings below 1 μm, the minority‐carrier lifetime is invariant, suggesting that the interfacial recombination velocity decreases with decreasing heterojunction spacing. No such effect is observed in single‐heterojunction diodes.
107 citations
TL;DR: In this article, a detailed study of the on state of amorphous threshold switches has been performed, where the authors determined the size of the conducting filament as a function of operating current.
Abstract: A detailed study of the on state of amorphous threshold switches has been performed. Transient and steady‐state I‐V characteristics have been investigated as functions of film thickness, pore size, and electrode material. Velocity saturation effects in amorphous/crystalline Si heterojunctions and threshold recovery curves were also studied. It is found that the on‐state resistivity is approximately 0.08 Ω cm, independent of electrode material. The on state is that of a semiconductor whose electronic band structure and carrier mobility are essentially unchanged from the off state, but in which a concentration of about 7×1018 free electron/cm3 produces the high conductivity observed. The decay of the on state is due to a combination of diffusion of the free carriers out of the filament, together with direct carrier recombination. A major result of this work is the determination of the size of the conducting filament as a function of operating current. As expected, the current density in the filament is esse...
105 citations
TL;DR: In this article, the capacitancevoltage and forward biased current-voltage characteristics, electroluminescence (E.L) and photovoltaic effect of GaSe-SnO2 heterojunction diodes are measured.
Abstract: The capacitance-voltage (C-V) and forward biased current-voltage (I-V) characteristics, electroluminescence (E.L) and photovoltaic effect of GaSe–SnO2 heterojunction diodes are measured. SnO2 layer is deposited on the c-plane of GaSe by using the spray method. The C-V and I-V characteristics of these diodes reveal the existence of a high resistivity layer, probably due to the diffusion of Sn into GaSe. The width of this layer is about 2.6 µm. And the current transport mechanism at low voltage is space-charge-limited. The trap density and the energy level of the trap from the valence band estimated by Lampert theory are about 5×1013~1×1014 cm-3 and 0.4~0.6 eV, respectively. The electroluminescence spectra at 275 K show one emission band due to free exciton recombination.
94 citations
TL;DR: In this article, the difference in lattice parameter between the GaAs substrate and the aluminum-substituted epitaxic layer AlxGa1−xAs has been measured accurately on a double-crystal spectrometer for a series of compositions.
Abstract: Heterojunctions GaAs–AlxGa1−xAs involved in the elaboration of IR laser diodes have been studied. The difference in lattice parameter between the GaAs substrate and the aluminum-substituted epitaxic layer AlxGa1−xAs has been measured accurately on a double-crystal spectrometer for a series of compositions. These data coupled with radius of curvature determination have permitted calculation of the stress in the layer and the bulk lattice parameter of AlxGa1−xAs. characterization of the defects introduced during the liquid-phase epitaxy has been performed by X-ray topography.
79 citations
TL;DR: In this paper, the authors presented a first attempt to predict heterojunction band lineups from the bulk band structures of the participating semiconductors, without invoking free surface properties.
Abstract: We present a first attempt to predict heterojunction band lineups from the bulk band structures of the participating semiconductors, without invoking free surface properties Band structures and electrostatic potentials are calculated by a self‐consistent pseudopotential A simple electrostatic matching scheme lines up the electrostatic potentials, and through them the band structures Predicted lineups are in good qualitative agreement with known lineups, and even in some cases [particularly GaAs– (Al,Ga)As] in good quantitative agreement
78 citations
01 Oct 1976
TL;DR: In this article, the authors considered configurations of uniformly pumped semiconductor slabs that constitute the transmission medium of multilayered slab waveguides, whose boundaries are trapless heterojunctions.
Abstract: A state-of-the-art discussion of heterostructure injection lasers is presented. These lasers are first considered as configurations of uniformly pumped semiconductor slabs that constitute the transmission medium of multilayered slab waveguides, whose boundaries are trapless heterojunctions. Emphasis is on lasers whose electrically active and waveguiding layers are Al x Ga 1-x As or GaAs, although several other semiconductors are discussed. Single, double, and separate confinement hetrostructure lasers, all of which yield carrier and optical confinement normal to the plane of the heterojunctions, are described. Lateral electrical and optical confinement in various stripe geometry double-hetrostructure lasers is illustrated. In addition to the more common Fabry-Perot cavity lasers, there are now also several new varieties that use corrugated surfaces as Bragg gratings for internal distributed feedback or reflection. Some of these heterostructure lasers have permitted the demonstration of CW-room temperature injection lasers with low threshold current densities ( 105) h), and a considerable degree of control over modes and beam divergence. In addition, the use of heterostructures has permitted the demonstration of the first integratedoptical structures that include both active light generating and passive elements on a single chip.
Book•
01 Jan 1976
TL;DR: In this article, a variety of CdS/CdTe heterojunction solar cells have been prepared by the vacuum evaporation of n−CdS films onto single-crystal p−cdTe substrates, and the mechanisms controlling the dark junction current, photocarrier collection and photovoltaic properties with junction interface states present are modeled.
Abstract: A variety of CdS/CdTe heterojunction solar cells have been prepared by the vacuum evaporation of n‐CdS films onto single‐crystal p‐CdTe substrates. Comparisons have been made between cells prepared using different substrate resistivities, substrate surface preparations, and CdS film resistivities. The mechanisms controlling the dark junction current, photocarrier collection, and photovoltaic properties with junction interface states present are modeled. A solar efficiency of 7.9% under 85 mW/cm2 of solar simulator illumination was measured on a cell with an indium‐tin‐oxide coating and a glycerol antireflection coating.
TL;DR: In this article, a detailed study of AlxGa1−xAs/GaAs double heterojunction lasers combining very thin recombination regions (d?0.1 μm) with high Al concentration differences at the heterojunctions is presented.
Abstract: A detailed study is presented of AlxGa1−xAs/GaAs double heterojunction lasers combining very thin recombination regions (d?0.1 μm) with high Al concentration differences at the heterojunctions. These devices have exceptionally low threshold current densities (475–1000 A/cm2 depending on the structural details), which increase by a median value of 1.35 between 22 and 70 °C. The differential quantum efficiency decrease in that same temperature interval is small. The device parameters have been analyzed in terms of available theory connecting the radiation confinement to the width of the recombination region and the dielectric step at the heterojunctions. Both the threshold current density dependence on the width of the recombination region and the far‐field beam pattern are in reasonable agreement with theory. Assuming no change in carrier or optical flux confinement for large Al concentration differences, the temperature dependence of the threshold current density is found to be somewhat steeper than calcu...
TL;DR: In this article, the performance of LPE In1−xGaxP1−zAsz double heterojunction (DH) laser diodes at short wavelength is described (Jth ≥ 2×104 A/cm2, λ∼6470 A, heterobarrier ΔE∼137 meV).
Abstract: Pulsed room‐temperature operation of LPE In1−xGaxP1−zAsz double heterojunction (DH) laser diodes at short wavelength is described (Jth≲2×104 A/cm2, λ∼6470 A, heterobarrier ΔE∼137 meV). The differential quantum efficiency of these diodes is ηext∼5%, and is considered to be low because of large diode size, thick active region, probably some layer mismatch and growth defects, and relatively poor heat sinking. The temperature dependence of threshold current density (Jth∼J0 expT/T0, T0∼74 °K) is presented in the range 77–300 °K and is compared with similar diodes having smaller heterobarriers and which, as expected, exhibit poorer performance (smaller T0).
TL;DR: In this paper, the authors compared the performance of multilayer heterostructures (ML) grown by molecular beam epitaxy (MBE) that consist of many alternating thin layers of GaAs and AlxGa1−xAs.
Abstract: Optically pumped laser oscillation from multilayer heterostructures (ML) grown by molecular beam epitaxy (MBE) that consist of many alternating thin layers of GaAs and AlxGa1−xAs has been studied in some detail over the temperature range 7–300 K. These samples which have GaAs layers 100–200 A thick that act as one‐dimensional potential wells for electrons and holes have thresholds for lasing that are generally a factor of 2 or more higher than conventional comparable GaAs‐AlxGa1−xAs double heterostructures (DH) also grown by MBE. The quantum effects due to the GaAs wells of the ML samples are shown to exist under lasing conditions well above room temperature, but there is no evidence to date of the beneficial effects expected from the modified density of states of this type of structure. Also optically pumped conventional DH lasers grown by MBE and liquid phase epitaxy (LPE) have been compared. The DH lasers grown by MBE are found to have lasing thresholds that are consistently about a factor of 2 higher ...
TL;DR: In this paper, the lattice matched LPE quaternary alloy growth process is outlined, as well as the need for complete melt removal between the growth of each heterojunction layer.
Abstract: Improved yellow‐spectrum double‐heterojunction In1−xGaxP1−zAsz laser diodes constructed by LPE on VPE GaAs1−yPy substrates are described. The lattice‐matched LPE quaternary alloy growth process is outlined, as well as the need for complete melt removal between the growth of each heterojunction layer, which is more difficult for In‐rich melts than for Ga‐rich melts when lattice match is a problem. Over two times lower threshold current densities are demonstrated (Jth?3.6×103 A/cm2, λ?5920 A, 77 °K) than for the first reported diodes of this type. The temperature dependence of laser threshold current density is presented in the range 4.2–200 °K. The threshold current density can be approximated as Jth∝exp(T/T0) with T0?52 °K in the range 50–175 °K, which compares well with red‐orange AlGaAs double heterojunctions (T0?42 °K) having greater heterobarriers. Laser operation in the yellow‐orange portion of the visible spectrum at ∼200 °K is demonstrated. These results on thick (1.5 μm) active layer diodes, havin...
TL;DR: In this article, a model quantitatively explaining the experimental data for a MOS-type solar cell is presented, where transparent conducting films of indium-tin oxide (ITO) are sputtered onto wafers of single-crystalline Si.
Abstract: We have fabricated solar cells consisting of transparent conducting films of indium‐tin oxide (ITO) rf sputtered onto wafers of single‐crystalline Si. A model quantitatively explaining the experimental data for this MOS‐type solar cell is presented.
TL;DR: PbTe and Pb0.8Sn0.2Te epitaxial films have been grown on cleaved BaF2 substrates by a modified hot-wall technique.
Abstract: PbTe and Pb0.8Sn0.2Te epitaxial films have been grown on cleaved BaF2 substrates by a modified hot‐wall technique. Relatively fast growth rates of 3–5 μm/h have been used to prepare high‐quality epitaxial films between 5 and 13 μm in thickness. Both p‐ and n‐type films have been grown by temperature control of a separate Te reservoir included in the apparatus. Carrier concentrations and mobilities in the orders of 2×1016–7×1017/cm3 and 1–3.3×104 cm2/V sec, respectively, have been measured in the as‐grown films at 77 K. Pb0.8Sn0.2Te homojunction and PbTe‐Pb0.8Sn0.2Te heterojunction layers have been prepared. Diode elements engraved in the layers by mesa etching have shown R0A products between 19 and 38 Ω cm2 for heterojunction structures at 77 K.
TL;DR: In this paper, a phenomenological model for the electrical conductivity in polycrystalline semiconductors is presented, using the assumption that an isotype heterojunction with a certain interface state density exists at the grain-intergrain domain interface.
TL;DR: In this paper, double heterojunction PbS−PbS1−x−x sex-PBS laser diodes have been fabricated by hot-wall molecular beam epitaxy.
Abstract: Double heterojunction PbS‐PbS1−xSex‐PbS laser diodes have been fabricated by hot‐wall molecular beam epitaxy. The lasers had stripe geometry of 100‐μm width formed by MgF2 passivation. Structures for electron and hole injection, respectively, are compared. Devices with 1‐μm‐thick active layers showed threshold current densities of about 400 A/cm2 at 77 K and 1.4×104 A/cm2 at 190 K. cw operation could be realized up to 96 K.
TL;DR: In this article, the maximum attainable efficiency for the conversion of solar energy into electric energy was calculated as a function of the two semiconductor band gaps, E g 1 and E g 2, and of two material parameters, a 1 and a 2.
Patent•
26 Oct 1976
TL;DR: In this article, a photoelectron emission device comprising mixed crystals of two or more different different semiconductors forming a heterojunction with direct transition type defining a first region in which may be excited by photoelectrons and an indirect transition type defined a second region whose forbidden band gap is wider than that of the first region and the surface of which is a photo-electron surface.
Abstract: Semiconductor photoelectron emission device comprising mixed crystals of two or more different semiconductors forming a heterojunction with direct transition type defining a first region in which may be excited by photoelectrons and an indirect transition type defining a second region whose forbidden band gap is wider than that of the first region and the surface of which is a photoelectron emission surface.
TL;DR: In this article, the authors report room temperature operation of a buried heterostructure distributed feedback diode laser, which operates in a single TE polarized longitudinal mode over a temperature range from 232 to 324 K and exhibits a temperature sensitivity of 0.72 A/K.
Abstract: We report room‐temperature operation of a buried heterostructure distributed feedback diode laser. The device operates in a single TE polarized longitudinal mode over a temperature range from 232 to 324 K and exhibits a temperature sensitivity of 0.72 A/K. In comparison, the variation for a similar Fabry‐Perot diode is 3.4 A/K.
TL;DR: In this paper, an exponential trap distribution is suggested and trap density calculations agree with literature results, showing that chalcogenide glass/silicon structures behave like ideal abrupt heterojunctions.
Abstract: Sevroal properties of glass‐silicon heterojunctions have been studied as a function of glass composition. Oxide and chalcogenide glasses of both insulating and semiconducting behavior were investigated. The current‐voltage characteristic indicates space‐charge‐limited currents in the glass film regardless of composition. An exponential trap distribution is suggested and trap density calculations agree with literature results. Capacitance‐voltage measurements show that chalcogenide glass/silicon structures behave like ideal abrupt heterojunctions.
TL;DR: In this article, a simple model satisfactorily describes the phase equilibria of the system near the InP corner of the phase diagram, in particular the solidus isotherms are in good agreement with calculation.
TL;DR: In this article, single crystalline CdSe, ZnSe and Zn x Cd 1-x Te layers with thickness of several tens of microns have been obtained on ZnTe and znSe substrates using the liquid-phase epitaxy technique.
TL;DR: In this paper, measurements of the diffusion potential, depletion layer width, and bias dependence of quantum efficiency for n−CdSe/p−ZnTe heterojunctions are used to construct a band diagram for the junction and to propose a current transport model.
Abstract: Measurements of the diffusion potential, depletion layer width, and bias dependence of quantum efficiency for n‐CdSe/p‐ZnTe heterojunctions are used to construct a band diagram for the junction and to propose a current transport model. A new value of the electron affinity of CdSe is indicated by measurements of the open‐circuit voltage at low temperatures and high intensities. The saturation current density J0 is controlled by a thermal activation energy of 0.8 eV, corresponding to electron flow to the interface where recombination occurs through interface states. Performance as photovoltaic cells is limited by the short diffusion length of holes in CdSe.
Patent•
IBM1
TL;DR: In this paper, the authors proposed to constrain the liquid phase epitaxial growth to proceed only upon a (311B) surface of a crystalline semiconductor having diamond, zinc-blende, or chalcopyrite structure.
Abstract: Practice of this disclosure reduces the concentration of intrinsic defects heretofore grown into semiconducting materials. Thereby, the operational lifetime is increased of heterostructure junction light emitting or responding or modulating devices which are fabricated in accordance with principles of the disclosure. Illustratively, the operational lifetime of a heterostructure junction laser device thus fabricated is extended. This improvement in operational lifetime of the device is attained by constraining growth, e.g., liquid phase epitaxial growth, of the several layers of semiconducting materials which form such a device to proceed only upon unreconstructed surface layers. Illustratively, such an unreconstructed surface is any one of the set of (311) surfaces of a crystalline semiconductor having diamond, zinc-blende, or chalcopyrite structure. In particular, the operational lifetime of GaAlAs double heterostructure junction lasers is increased by constraining the liquid phase epitaxial growth to proceed only upon a (311B), i.e., an As terminated (311), surface so that respective interfaces between layers of the resultant devices are (311) crystal planes.
TL;DR: In this paper, a threshold-switching-type chalcogenide glass was used as the emitter, with a p-type crystalline-silicon base and an n-type silicon collector.
Abstract: The characteristics of a new hybrid amorphous-crystalline three-terminal device are described in detail. The device uses a threshold-switching-type chalcogenide glass as the emitter, with a p-type crystalline-silicon base and an n-type silicon collector. When the amorphous emitter is in the off state, the small-signal current gain is significantly smaller than unity. However, once the voltage across the glass is sufficient to produce the on state, the device operates as a transistor with gains well in excess of unity. (Small-signal gains of up to 15 have already been observed in unoptimized configurations.) Under certain conditions, the high-gain on state can be preserved after the switching pulse is removed, suggesting memory-type applications. Previous results on amorphous-crystalline heterojunctions are used to construct a band model for the transistor. This model is used to analyze the steady-state and pulsed-mode characteristics of the device. Recent studies of the on-state current density and carrier concentration are used to calculate the expected gain as a function of current and base doping concentration, with results in good agreement with the experimental data. The behavior of the devices provides another confirmation of the electronic nature of threshold switching in chalcogenide glasses.
Patent•
06 Jan 1976
TL;DR: In this article, the authors show that the conduction band energy level of the wider bandgap material is at least as high as that of the narrower bandgap materials at electrical neutrality.
Abstract: A semiconductive heterojunction device particularly useful as a photovoltaic device such as a solar cell comprises a heterojunction formed between a first layer of semiconductor material exhibiting one type of electronic conductivity (N or P) and a second layer of a compositionally different material exhibiting the other type of electronic conductivity (P or N), which second layer has an energy bandgap relatively wider than that of the semiconductor material and an electron affinity less than or equal to the electron affinity of the semiconductor. Preferably, the wider bandgap material is a glassy amorphous material which possess or is doped to possess a low resistivity below about 107 ohm-cm. In devices employing N-type wider bandgap layers, the conduction band energy level of the wider bandgap material is preferably at substantially the same energy level as the conduction band energy level of the narrower bandgap material at electrical neutrality. In devices employing P-type wider bandgap layers, the valence band energy level of the wider bandgap material is preferably at substantially the same energy level as the valance band energy level of the narrower bandgap material.