Showing papers on "Heterojunction published in 1975"
TL;DR: In this paper, the evolution of resonantly split discrete well states into the lowest band of a one-dimensional superlattice was demonstrated via low-temperature optical-absorption measurements on ultrathin, coupled potential wells in molecular-beam-grown GaAs heterostructures.
Abstract: We demonstrate, via low-temperature optical-absorption measurements on ultrathin, coupled potential wells in molecular-beam-grown ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$-GaAs heterostructures, the evolution of resonantly split discrete well states into the lowest band of a one-dimensional superlattice. Both electron and hole superlattices appear to be practical.
294 citations
TL;DR: In this article, optically pumped laser oscillation from multilayer heterostructures consisting of alternating layers of GaAs and Al0.2Ga0.8As was reported.
Abstract: We report optically pumped laser oscillation from multilayer heterostructures consisting of alternating layers of GaAs and Al0.2Ga0.8As. Very thin GaAs layers (50−500 A) exhibit one−dimensional bound states above the band gap of bulk GaAs. The laser oscillation occurs at energies which are slightly below the exciton associated with the lowest energy n=1 bound state.
180 citations
Patent•
07 Mar 1975TL;DR: In this paper, a heterostructure semiconductor laser comprising a pair of wide bandgap layers having an active region sandwiched therebetween is characterized in that the active region includes a plurality of thin narrow bandgap active layers interleaved with a relatively wider bandgap passive layers.
Abstract: Described is a heterostructure semiconductor laser comprising a pair of wide bandgap layers having an active region sandwiched therebetween characterized in that the active region includes a plurality of thin narrow bandgap active layers interleaved with a plurality of thin relatively wider bandgap passive layers. The passive layers are thin enough (e.g., about 10-500 Angstroms) to permit electrons to distribute among the active layers either by tunneling through, or by hopping over, the energy barriers created by the passive layers. The active layers are thin enough (e.g., about 10-500 Angstroms) to separate the quantum levels of electrons confined therein. These lasers exhibit wavelength tunability by changing the thickness of the active layers. Also described is the possibility of threshold reductions resulting from modification of the density of electron states.
125 citations
TL;DR: In this article, two different types of dislocation networks have been observed close to the active region of the degraded device having Burgers vectors of (a/2) 〈011〉 and a〈001〉.
Abstract: Transmission electron microscopy has been used to study the defects associated with the degradation of broad−contact geometry double−heterostructure lasers. Two different types of dislocation networks have been observed close to the active region of the degraded device having Burgers vectors of (a/2) 〈011〉 and a〈001〉. Both networks have been shown to be of interstitial character.
101 citations
TL;DR: In this article, a separate-confinement heterostructure injection laser with periodic corrugations in the optical cavity was prepared by a hybrid liquid phase epitaxy and molecular beam epitaxy (MBE) growth process.
Abstract: Separate‐confinement heterostructure injection lasers with periodic corrugations in the optical cavity were prepared by a hybrid liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE) growth process. The N‐Al0.3Ga0.7As, N‐Al0.12Ga0.88As, p‐GaAs active layer, and P‐Al0.12Ga0.88As layers were grown by LPE, a 0.3748‐μm periodic corrugation was ion milled into the P‐Al0.12Ga0.88As layer, and then the P‐Al0.3Ga0.7As and p‐GaAs top layers were grown over the corrugation by MBE. The temperature dependence of the lasing wavelength between 12.6 and 24.8 °C demonstrated the behavior expected for a distributed‐feedback laser. The threshold current density was 2.2 kA/cm2 at room temperature.
95 citations
TL;DR: In this paper, a model is proposed showing how restricted climb of dislocations threading the active region of a degraded double heterojunction GaAs laser could explain the growth of dislocation networks of the types (a, and b) and would account for the observed preferred ⟨100⟩ and ⟩110≵ orientations of darkline defects.
Abstract: Detailed transmission electron microscopy contrast analysis is presented revealing the interstitial nature of the defect networks associated with the active region of a degraded double heterojunction GaAs laser. Three different dislocation networks with Burgers vectors of (a) a/2[011] inclined at 45° to the (001) junction plane, (b) a/2[110] lying in the junction plane and (c) a[001] normal to the junction plane have been observed and investigated. A model is proposed showing how restricted climb of dislocations threading the active region could explain the growth of dislocation networks of the types (a) and (b) and would account for the observed preferred ⟨100⟩ and ⟨110⟩ orientations of darkline defects.
93 citations
TL;DR: In this article, a GaAs/GaAlAs/AlGaAs/glass heterostructure has been constructed on a gaAs susbtrate, bonded to 7056 Corning glass, and the substrate and first AlGaAs removed chemically, utilizing the differential etching characteristics of GaAs and AlGAAs in NH4OH−H2O2 and HF solutions.
Abstract: A GaAs/GaAlAs/GaAs/GaAlAs heterostructure has been prepared on a GaAs susbtrate, bonded to 7056 Corning glass, and the substrate and first AlGaAs removed chemically, utilizing the differential etching characteristics of GaAs and AlGaAs in NH4OH−H2O2 and HF solutions. The resulting structure of GaAs/AlGaAs/glass has excellent layer morphology, uniform thickness, and good transmission photocathode performance.
87 citations
TL;DR: In this paper, an injection laser is described in which a semicircular GaAs active region is completely surrounded by Ga1−xAlxAs by using selective etching and a single liquid-phase epitaxial growth.
Abstract: An injection laser is described in which a semicircular GaAs active region is completely surrounded by Ga1−xAlxAs by using selective etching and a single liquid‐phase epitaxial growth.The active region dimensions can be made much more symmetric than those obtained with conventional stripe geometry lasers resulting in improved optical characteristics and low room‐temperature threshold currents.
81 citations
TL;DR: In this article, double-sided heterostructures were prepared from four-component solid solutions GaxIn1-xAsyP1-y(λ=1.02 μ) and AlxGa1−xSbyAS1−y (λ=0.945 μ).
Abstract: Double-sided heterostructures were prepared from four-component solid solutions GaxIn1–xAsyP1–y(λ=1.02 μ) and AlxGa1–xSbyAS1–y(λ=0.945 μ). In the former system the problem of compatability of the lattices was solved by adding Ga and As to InP in amounts which ensured that the lattice period was the same (because of the opposite influence of these impurities). Indium phosphide was used as the wide-gap layer. The resultant laser heterostructure was the first system not based on the mutual replacement of Al and Ga, in contrast to earlier heterolasers and to the second investigated system (AlxGa1–xSbyAS1–y).
75 citations
TL;DR: In this article, a simplified method for calculating the energy band profiles of graded-gap heterojunctions, based on the generalized model of Oldham and Milnes, is presented, where the profiles are derived by superposing an energy band grading function and the electrostatic potential in the heterojunction.
Abstract: A simplified method for calculating the energy band profiles of graded-gap heterojunctions, based on the generalized model of Oldham and Milnes, is presented. The profiles are derived by superposing an energy band grading function and the electrostatic potential in the heterojunction. The latter is obtained by using the depletion layer approximation as for conventional p-n homojunctions. The energy band profiles of hypothetical p(GaAs)-n(Al0·4Ga0·6As) heterojunctions are calculated using the simplified method. For small grading layer widths, the results are in good agreement with the generalized model. The barrier lowering factor η as a function of the graded layer width l is calculated for such heterojunctions. It is found, for acceptor and donor densities of 1018 and 1016 cm−3 respectively, that the barrier height is reduced from 0·47 eV to zero as l increases from zero (abrupt case) to ≈300 A. The applications of these analyses to practical heterojunctions are discussed.
74 citations
TL;DR: In this article, a theory of the band structure of semiconductor superlattices has been developed for both the direct-bandgap and indirect-band-gap barrier layers taking into account the multivalley and nonparabolic band structure.
Abstract: A theory of the band structure of semiconductor superlattices has been developed for both the direct-band-gap and indirect-band-gap barrier layers taking into account the multivalley and nonparabolic band structure of the materials forming the superlattice. For direct-band-gap barrier layers the nonparabolicity in the band structure may alter the electronic energy levels measured from the bottom of the potential wells by as much as 26%. On the other hand for indirect-band-gap barrier layers the alteration due to the nonparabolicity is about 14%. It is also found that even for indirect-band-gap barrier layers the band structure is mainly determined by the states corresponding to the direct-gap minimum. Energy levels calculated on the basis of the theory presented are also found to agree with those obtained in recent experiments with double-barrier heterostructures.
TL;DR: A thin insulating layer at the material interface of a heterojunction solar cell can cause a suppression of photocurrent, which increases with increasing illumination intensity and interfacial layer thickness as discussed by the authors.
Abstract: A thin insulating layer at the material interface of a heterojunction solar cell can cause a suppression of photocurrent. This photocurrent suppression increases with increasing illumination intensity and interfacial layer thickness. Although the presence of such an interfacial layer can increase the conversion efficiency of solar cells at low illumination intensities, the photocurrent suppression effect precludes its use in systems using appreciable solar concentration.
TL;DR: In this paper, a graded-band-gap pGa1−xAlxAs−nGaAs solar cell is fabricated by utilizing the diffusion of Al in the Ga melt.
Abstract: The theoretical spectral response of the graded‐band‐gap pGa1−xAlxAs‐nGaAs solar cell is calculated by solving the continuity equations. The electric fields produce a collection efficiency two times larger than that of the abrupt heterojunction diodes at wavelengths less than 700 nm for surface recombination velocities of 106–107 cm/sec. The graded‐band‐gap diode can be operated at high frequencies because of the reduced transit time of minority carriers in the p‐type layer. A graded‐band‐gap pGa1−xAlxAs‐nGaAs solar cell is fabricated by utilizing the diffusion of Al in the Ga melt. The gradient of the energy gap is evaluated by photoresponse and photoluminescence measurements. The photoluminescence shows a broad emission peak from 700 to 800 nm at 77 K.
TL;DR: In this article, the basic factors that enter into the successful operation of single crystal heterojunction devices, with an emphasis on the role of defects, are reviewed. The devices discussed include laser diodes, solar cells and electron emitters using negative electron affinity surfaces.
Abstract: Basic factors are reviewed that enter into the successful operation of single crystal heterojunction devices, with an emphasis on the role of defects. The devices discussed include laser diodes, solar cells and electron emitters using negative electron affinity surfaces.
TL;DR: In this article, the characteristics of the heterojunction transistors were examined as functions of the injection current density and the temperature, and it was shown that the transistors have a common emitter current gain β of up to 350.
Abstract: n (GaAl)As‐pGaAs‐nGaAs heterojunction transistors were fabricated by the liquid‐phase epitaxial technique, where two kinds of etchants were used to expose the pGaAs base region. The characteristics of the heterojunction transistors are examined as functions of the injection current density and the temperature. Electrical measurements showed that the transistors have a common emitter current gain β of up to 350. The defect current component in the emitter heterojunction is the recombination current in the depletion region.
TL;DR: In this paper, a new type of AlAs-GaAs semiconductor heterojunction laser with small radiation divergence has been proposed, where the angle of divergence of the radiation in this case was equal to 0.5° both with optical and injection pumping.
Abstract: In AlAs-GaAs semiconductor heterojunction lasers, due to the interaction of the waveguide modes with a diffraction grating on the surface of the waveguide layer, output of coherent radiation has been obtained through the plane parallel to the layer. The angle of divergence of the radiation in this case was equal to 0.5° both with optical and injection pumping. The possibility of fabricating a new type of semiconductor laser with small radiation divergence has been proven experimentally.
TL;DR: In this paper, an analysis of the scattering in both three and five-layer heterostructures is presented, and curves are derived relating the absorption coefficient with the dielectric-constant step at the Waveguide Wall, the active-layer thickness, and the magnitude of the roughness.
Abstract: The optical-absorption loss in (GaAl)As/GaAs heterostructure lasers with narrow active layers and passive layers doped below 5 \times 10^{17} cm-3should be less than 5 cm-1. Measurements which have been made on a variety of three- and five-layer lasers have seldom shown such low figures. Optical-scattering loss at imperfections in the heterostructure interface could account for the discrepancy. An analysis of the scattering in both three- and five-layer heterostructures is presented. Curves are derived relating the absorption coefficient with the dielectric-constant step at the Waveguide Wall, the active-layer thickness, and the magnitude of the roughness. Measured losses as high as 12 cm-1can be accounted for by a roughness amplitude of only 0.01 μm.
TL;DR: In this article, a depletion layer bordering a semiconducting channel is shown to be partially depleted if the space−charge region penetrates to another depletion layer at the other side of the channel, i.e., if the channel is partially depleted.
Abstract: C−V analysis applied to a depletion layer bordering a semiconducting channel does not provide the true impurity distribution if the space−charge region penetrates to another depletion layer at the other side of the channel, i.e., if the channel is partially depleted. Cases in point are an epitaxial semiconducting channel on a semi−insulating chromium−doped gallium arsenide substrate; an n−channel on a p−substrate; and a heterojunction of a semiconducting epitaxial layer on an insulating substrate with interface states causing depletion.
TL;DR: In this paper, a p−n heterojunction laser structure of InxGa1−xAs/InyGa 1−yP with threshold current densities as low as 15'000 A/cm2 at room temperature and 1000 A/ cm2 at 77'°K was obtained.
Abstract: Vapor‐grown p‐n heterojunction laser structures of InxGa1−xAs/InyGa1−yP have been prepared with laser threshold current densities as low as 15 000 A/cm2 at room temperature and 1000 A/cm2 at 77 °K. Emission wavelengths between 1.025 and 1.15 μm have been obtained at 300 °K.
TL;DR: In this paper, double-heterostructure (DH) lasers with Si-doped n-type active layers have been prepared by molecular-beam epitaxy (MBE) and the laser properties evaluated.
Abstract: GaAs-Al x Ga 1-x As double-heterostructure (DH) lasers with Si-doped n-type active layers have been prepared by molecular-beam epitaxy (MBE) and the laser properties evaluated. With 0.2-μm-thick active layers and 300-μm cavity lengths, typical room-temperature threshold current densities J th of 5.0 \times 10^{3} A/cm2and best values of 2.5 \times 10^{3} A/cm2have been obtained. Stripe-geometry devices were run CW up to 9°C. Photoluminescence (PL) studies of single layers grown with the donors Si, Ge, and Sn show that the luminescent intensity for MBE n-type layers depends on the substrate temperature during growth. The PL intensity for Sn-doped MBE layers was greater than for high-quality Sn-doped liquid-phase-epitaxial layers.
TL;DR: In this paper, the normal alloying process is treated as an epitaxy process, where Ga and As are supplied separately by evaporation together with the normal contact metals and by overpressure, respectively.
Abstract: Ohmic contacts of superior quality are produced by treating the normal alloying process as an epitaxy process, where Ga and As are supplied separately by evaporation together with the normal contact metals and by overpressure, respectively. New device fabrication methods based on this new scheme are the production of shallow p-n junctions, shallow heterojunctions, thin ternary semiconductor layers with different bandgaps from that of the bulk, and multiple structures. By using photoresist, complete regrowth patterns as used for IC's should be possible. The types of devices where these developments should be of interest are solar cells, light-emitting IC patterns, even with different light colors on one chip, Gunn devices, BARITT's, MESFET's, Schottky CCD's, heterojunction bipolar transistors, etc.
TL;DR: In this article, a backside-illuminated Pb1−xSnxTe heterojunction was constructed, where the radiation incident upon the sloping sides of the mesa is internally reflected into the junction region due to the index of refraction mismatch between air and PbTe; thus with this design the optical area which gives rise to the signal current is larger than the electrical area which is the source of noise.
Abstract: The need for a long−wavelength infrared detector that makes more efficient use of the available radiation has led us to construct a backside−illuminated Pb1−xSnxTe heterojunction in which the radiation passes through a transparent substrate and is absorbed in the active region behind a p−n junction. This device permits a selectivity in the spectral bandwidth of the device due to the short−wavelength cut−on properties of the transparent PbTe substrate or an epitaxial Pb1−xSnxTe filter layer. Additionally, an effective increase in optical area is achieved because the radiation incident upon the sloping sides of the mesa is internally reflected into the junction region due to the index of refraction mismatch between air and PbTe; thus with this design the optical area which gives rise to the signal current is larger than the electrical area which is the source of noise. Laboratory measurements on devices of this construction verify these properties and show that a peak Dλ greater than 1011 cm Hz1/2 W−1 has b...
Patent•
14 Aug 1975TL;DR: In this paper, a wide-gap collector and an isotype emitter with different impurity doping levels are shown to be present in heterojunction devices including heterotransistors and heterodiodes, which exhibit improved highfrequency, efficiency, and power characteristics.
Abstract: Heterojunction devices including heterotransistors and heterodiodes are disclosed which exhibit improved high-frequency, efficiency, and power characteristics. The heterotransistor in one embodiment includes a wide-gap collector and in another embodiment includes a wide-gap isotype emitter having regions of different impurity doping levels. A heterodiode includes a similar wide-gap isotype emitter. Also disclosed are a heterojunction microwave diode and two types of heterojunction photocathodes. The microwave diode and one of the photocathodes are characterized by the occurrence of avalanche at the heterojunction.
IBM1
TL;DR: In this paper, a new process for stripe formation in double-heterostructure GaAs/GaAlAs injection lasers is described, which uses oxygen-ion implantation to form the stripe through a chemical doping effect.
Abstract: We describe a new process for stripe formation in double-heterostructure GaAs/GaAlAs injection lasers This process, which uses oxygen-ion implantation to form the stripe through a chemical doping effect, has several advantages over alternative methods, both with respect to device processing and device properties and has produced high yields of CW room-temperature lasers We present the details of the device structure and fabrication processes The results of annealing studies, optical measurements, and lifetesting are described
TL;DR: In this article, a selective multilayer epitaxial growth of GaAs-Ga1-xAlxAs through stripe openings in Al2O3 mask is reported.
Abstract: Selective multilayer epitaxial growth of GaAs-Ga1–xAlxAs through stripe openings in Al2O3 mask is reported. The technique results in prismatic layers of GaAs and Ga1–xAlxAs "embedded" in each other and leads to controllable uniform structures terminated by crystal faces. The crystal habit (shape) has features which are favorable for fabrication of cw injection lasers, laser arrays, and integrated optics components which require planar definition.
Patent•
05 Jun 1975TL;DR: In this article, a photo-detector diode is used which comprises a heterojunction of two epitaxial layers of differing compositions of a ternary III-V semiconductive alloy, such that the outer layer will serve as a radiation-admitting window as well as physical protection for the underlying absorbing layer in the so-called direct photodetector dode configuration.
Abstract: GROWTH AND OPERATION OF A STEP-GRADED TERNARY III-V HETEROJUNCTION P-N DIODE PHOTODETECTOR Abstract of the Disclosure In an infrared photodetection apparatus a photo-detector diode is used which comprises a heterojunction of two epitaxial layers of differing compositions of a ternary III-V semiconductive alloy, such that the outer layer will serve as a radiation-admitting window as well as physical protection for the underlying absorbing layer in the so-called direct photodetector diode configuration. The ternary alloy illustratively includes two metallic group III elements such as indium and gallium; but the principle can be extended to ternary alloys including two group Velements, such as arsenic and antimony. Further, quaternary alloys of III-V elements can be employed. The absorbing layer is selected to be substantially intrinsic. The latter is the case for an n-type layer of InxGa(1-x)As. Matching of this absorbing layer to a gallium arsenide substrate is achieved by a plurality of step-graded composi-tion layers of indium gallium arsenide.
TL;DR: In this paper, the relationship between the internal laser absorption and structural parameters appropriate for CW room-temperature lasers was analyzed. And the design curves were used to predict the gain required at threshold for a broad range of structural parameters of interest.
Abstract: Theoretical calculations are presented showing the relationship between the internal laser absorption and structural parameters appropriate for CW room-temperature lasers. These diodes have submicron-thick recombination regions, and very small spacings between the heat sink and the recombination region to minimize the thermal resistance. The optical loss is shown to be strongly dependent on the degree of radiation confinement to the active region. In particular, absorption in the surface GaAs layer providing the ohmic contact becomes very significant when the intermediate (AlGa)As layer is reduced below about 1 μm. It is further shown that excessive penetration into the GaAs regions gives rise to anomalies in the far-field radiation profiles in the direction perpendicular to the junction plane. Proper design of the internal structure of the laser avoids large increases of the threshold current density as well as large decreases in the external differential quantum efficiency from interaction with the contact layer. The design curves presented can be used to predict the gain required at threshold for a broad range of structural parameters of interest in low-threshold laser design.
TL;DR: In this article, a stripe geometry laser is demonstrated in which current confinement is achieved by selective diffusion of the n-type substrate prior to growth of the GaAs/GaAlAs heterostructure layers.
Abstract: A different type of stripe-geometry laser is demonstrated in which current confinement is achieved by selective diffusion of the n-type substrate prior to growth of the GaAs/GaAlAs heterostructure layers. This structure exhibits low room-temperature threshold currents resulting from the small lateral-current spreading from the edges of the stripe. Lowest order transverse-mode operation is achieved for stripe widths of 10μm.