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24 Dec 1990

Volume 57, Issue 26, pp. 2745-2861

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Maskless laser interferometric monitoring of InP/InGaAsP heterostructure reactive ion etching

Todd R. Hayes, P. A. Heimann, V. M. Donnelly, and K. E. Strege

Appl. Phys. Lett. 57, 2817 (1990); http://dx.doi.org/10.1063/1.103751 (3 pages) | Cited 18 times

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Infrared laser interferometry is used to measure etch rate, measure wafer temperature, and identify heterostructure layers in situ during reactive ion etching, with or without masked regions. Interference between reflections from the etching wafer surface, buried heterointerfaces, and polished wafer back allows etch rate monitoring and endpoint determination. Changes in the optical path length that occur as a wafer heats and cools upon processing also produce reflected intensity oscillations that allow determination of the process‐induced change in wafer temperature. We also show that λ=0.6238 μm light can be used to monitor optically thin heterostructure layers with enhanced depth resolution over infrared light.
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07.60.Ly Interferometers
81.65.-b Surface treatments
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Observation of charge storage and intersubband relaxation in resonant tunneling via a high sensitivity capacitive technique

E. F. Schubert, Federico Capasso, A. L. Hutchinson, S. Sen, and A. C. Gossard

Appl. Phys. Lett. 57, 2820 (1990); http://dx.doi.org/10.1063/1.103752 (3 pages) | Cited 7 times

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In suitably designed resonant tunneling double barriers the capacitance‐voltage curve exhibits well‐defined features corresponding to the charging and discharging of the quantum well. From the bias dependence of the electron density in the well we find that in our thick parabolic wells, electrons tunneling into the excited states relax to the lowest subband and sequentially tunnel out. Our experiments allow us to obtain the charge density accumulated in the well and the tunneling escape rate of electrons out of the well.
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73.40.Gk Tunneling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Low‐density high‐mobility electron gas in wide parabolic GaAs/AlxGa1−xAs wells

P. F. Hopkins, A. J. Rimberg, E. G. Gwinn, R. M. Westervelt, M. Sundaram, and A. C. Gossard

Appl. Phys. Lett. 57, 2823 (1990); http://dx.doi.org/10.1063/1.103753 (3 pages) | Cited 14 times

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Remotely doped wide parabolic GaAs/AlxGa1−xAs wells are used to create thick (≳ 1000 Å) layers of high‐mobility (≳ 2×105 cm2/V s) electron gas with three‐dimensional densities below (by a factor ∼3) the metal‐insulator transition for doped GaAs. The temperature dependences of the Hall mobility and sheet density show no qualitative changes in a series of three samples spanning the metal‐insulator transition. Shubnikov–de Haas oscillation measurements are used to determine the width of the electron gas layers.
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72.20.Fr Low-field transport and mobility; piezoresistance
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Ballistic electron studies and modification of the Au/Si interface

A. Fernandez, H. D. Hallen, T. Huang, R. A. Buhrman, and J. Silcox

Appl. Phys. Lett. 57, 2826 (1990); http://dx.doi.org/10.1063/1.103754 (3 pages) | Cited 18 times

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The Au/Si(111) interface has been investigated with ballistic electron emission microscopy. The Schottky barrier (SB) height and ballistic transmittance have been measured on interfaces which have been prepared with different types of monolayer‐level dopants. Transmission rates but not the SB are found to depend strongly on the resulting degree of interdiffusion of the Au and Si at the interface. An irreversible modification in the transport properties of the buried interface can occur when the system is stressed with electrons injected at several volts above the Schottky barrier.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
73.30.+y Surface double layers, Schottky barriers, and work functions
61.05.J- Electron diffraction and scattering
73.40.Ns Metal-nonmetal contacts

Electroreflectance and photoluminescence study of the effect of hydrogen on heavily doped GaAs/AlGaAs structures

D. Yang, J. W. Garland, P. M. Raccah, C. Coluzza, P. Frankl, M. Capizzi, F. Chambers, and G. Devane

Appl. Phys. Lett. 57, 2829 (1990); http://dx.doi.org/10.1063/1.103755 (3 pages) | Cited 12 times

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Highly doped semiconducting heteroepitaxial structures are commonly found in advanced devices. It is difficult to interpret quantitatively the results of optical measurements on such structures because the strong built‐in electric fields present invalidate the low‐field theories usually used to interpret those results. We have studied by electrolyte electroreflectance and photoluminescence a GaAs/AlGaAs resonant tunneling structure with a highly n‐doped GaAs substrate and cap, before and after hydrogenation. We also have developed a new, improved microscopic theoretical treatment of the effects of strong fields on the local dielectric function and have used that treatment to evaluate quantitatively the effect of hydrogenation on the densities of shallow donor levels and of deep traps in the GaAs cap and to find the interface charges and band‐pinning levels in the resonant tunneling junction.
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78.20.Jq Electro-optical effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.55.Cr III-V semiconductors

Noncontact energy level analysis of metallic impurities in silicon crystals

Y. Kirino, A. Buczkowski, Z. J. Radzimski, G. A. Rozgonyi, and F. Shimura

Appl. Phys. Lett. 57, 2832 (1990); http://dx.doi.org/10.1063/1.103756 (3 pages) | Cited 16 times

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Noncontact laser/microwave deep level transient spectroscopy (LM‐DLTS) based on the measurement of microwave reflection power as a function of temperature has been developed and applied to Czochralski silicon crystals intentionally contaminated with selected metals during crystal growth. The energy levels related to these metallic impurities in p‐type silicon have been obtained on bare silicon for the first time without any electrode contact or special sample preparation. The data agree in very satisfactory fashion with results obtained by conventional DLTS.
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71.55.Ht Other nonmetals
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors

Theoretical gain in strained InGaAs/AlGaAs quantum wells including valence‐band mixing effects

S. W. Corzine, R. H. Yan, and L. A. Coldren

Appl. Phys. Lett. 57, 2835 (1990); http://dx.doi.org/10.1063/1.103757 (3 pages) | Cited 62 times

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In this letter, we present the first detailed theoretical study of gain in strained InGaAs/AlGaAs quantum wells, taking into account the complex nature of the valence‐subband structure, which must be included in any realistic model. We first compare the material gain as a function of carrier and radiative current density for a strained and unstrained quantum well. We then present calculations of theoretical differential gain, carrier density, and radiative current density at transparency as a function of indium mole fraction in the well.<lz> <lz> <lz>
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Bk General theory, scattering mechanisms

Ultrafast initial relaxation of hot electrons and holes in tetrahedral semiconductors via deformation potential interaction: Theory and experiment

Stefan Zollner, Sudha Gopalan, Miquel Garriga, Josef Humlíček, Luis Viña, and Manuel Cardona

Appl. Phys. Lett. 57, 2838 (1990); http://dx.doi.org/10.1063/1.103758 (3 pages) | Cited 12 times

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The broadenings of the E1 and E1+Δ1 interband critical points can be understood as lifetime effects due to the ultrafast relaxation of the photoexcited hot holes. The contributions to these broadenings arising from the electrons in the conduction band are small, as intervalley scattering times are rather long. We have measured such broadenings in Si, Ge, α‐tin, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb with spectroscopic ellipsometry and compare them with calculations based on the deformation potential‐type electron‐phonon interaction in the rigid pseudo‐ion approximation.
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72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations
78.40.Fy Semiconductors
07.60.Fs Polarimeters and ellipsometers
78.47.-p Spectroscopy of solid state dynamics

InP/InGaAs double heterojunction bipolar transistors grown by metalorganic vapor phase epitaxy with sulfur delta doping in the collector region

E. Tokumitsu, A. G. Dentai, C. H. Joyner, and S. Chandrasekhar

Appl. Phys. Lett. 57, 2841 (1990); http://dx.doi.org/10.1063/1.104107 (3 pages) | Cited 16 times

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Sulfur δ doping in InP by metalorganic vapor phase epitaxy is reported. A peak carrier concentration of 7×1017 cm−3 with a full width at half maximum of 30 nm has been measured by the electrochemical capacitance‐voltage technique. It is shown that by inserting the δ‐doping spike in the collector region of InP/InGaAs double heterojunction transistors, the effective barrier height at the base‐collector interface can be reduced without increasing the base‐collector capacitance and excellent transistor characteristics can be realized.
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85.30.Pq Bipolar transistors
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Hydrolyzation oxidation of AlxGa1−xAs‐AlAs‐GaAs quantum well heterostructures and superlattices

J. M. Dallesasse, N. Holonyak, A. R. Sugg, T. A. Richard, and N. El‐Zein

Appl. Phys. Lett. 57, 2844 (1990); http://dx.doi.org/10.1063/1.103759 (3 pages) | Cited 325 times

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Data are presented on the conversion (selective conversion) of high‐composition (AlAs)x(GaAs)1−x layers, e.g., in AlxGa1−xAs‐AlAs‐GaAs quantum well heterostructures and superlattices (SLs), into dense transparent native oxide by reaction with H2O vapor (N2 carrier gas) at elevated temperatures (400 °C). Hydrolyzation oxidation of a fine‐scale AlAs(LB)‐GaAs(Lz) SL (LB +Lz≲100 Å), or random alloy AlxGa1−xAs (x≳0.7), is observed to proceed more slowly and uniformly than a coarse‐scale ‘‘alloy’’ such as an AlAs‐GaAs superlattice with LB + Lz≳200 Å.
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81.65.-b Surface treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Photofluxonic detection: A new mechanism for infrared detection in superconducting thin films

A. M. Kadin, M. Leung, A. D. Smith, and J. M. Murduck

Appl. Phys. Lett. 57, 2847 (1990); http://dx.doi.org/10.1063/1.103760 (3 pages) | Cited 33 times

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A new model is proposed in which a photon of energy E=hf is absorbed by a superconducting film to create a pair of equal and opposite fluxons (or vortices), each with quantized flux Φ0=h/2e. An applied current sweeps these fluxons to opposite edges of the film, causing a voltage pulse with time‐integrated magnitude Φ0, and leading to a time‐averaged voltage responsivity Rv = Φ0/E = 1/(2ef). This is directly analogous to photoconductive detection in a semiconductor via creation of electron‐hole pairs. Data on an ultrathin granular NbN film are presented which indicate a responsivity of 6000 V/W in red light, in agreement with the model. This is promising for the development of a sensitive, high‐speed infrared detector using thin films of either low or high Tc superconductors.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.78.-w Superconducting films and low-dimensional structures
85.60.Gz Photodetectors (including infrared and CCD detectors)

Preparation of NdBa2Cu3O7−δ films in ultrahigh vacuum with a NO2 supersonic molecular beam

Hidehiko Nonaka, Takashi Shimizu, and Kazuo Arai

Appl. Phys. Lett. 57, 2850 (1990); http://dx.doi.org/10.1063/1.104200 (3 pages) | Cited 16 times

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Superconducting NdBa2Cu3O7−δ thin films have been prepared in ultrahigh vacuum by the molecular beam epitaxy (MBE) method using a supersonic molecular beam of nitrogen dioxide as an oxidizing agent. A new type of supersonic molecular beam source has been developed, which has a liquid nitrogen trap for cryogenic pumping and is small enough in size to be installed in a conventional MBE system. Films with a transition temperature of about 30 K have been obtained in situ without post‐deposition annealing. Throughout deposition epitaxial growth of the films was observed in situ by reflection high‐energy electron diffraction.
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74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Bx Metals, semimetals, and alloys

High coercivity in Sm2Fe17Nx magnets

K. Schnitzke, L. Schultz, J. Wecker, and M. Katter

Appl. Phys. Lett. 57, 2853 (1990); http://dx.doi.org/10.1063/1.104202 (3 pages) | Cited 103 times

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Using mechanical alloying and a subsequent two‐step heat treatment we produced magnetically isotropic microcrystalline Sm2Fe17Nx samples with room‐temperature coercivities up to 24 kA/cm (30 kOe). The remanence and the energy product are equivalent to similarly prepared Nd‐Fe‐B samples, but the properties at elevated temperatures are superior because of the high Curie temperature of 470 °C and the large anisotropy field of 14 T at room temperature. From differential scanning calorimetry it is concluded that the 2:17 nitride is metastable. It decomposes into Sm nitride and α‐Fe above 600 °C.
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75.50.Vv High coercivity materials
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.50.Bb Fe and its alloys

Quantitative analysis of on bevel electrical junction shifts due to carrier spilling effects

T. Clarysse, W. Vandervorst, and A. Casel

Appl. Phys. Lett. 57, 2856 (1990); http://dx.doi.org/10.1063/1.103761 (3 pages) | Cited 11 times

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A quantitative comparison is made of the junction depths determined by spreading resistance (SR) and secondary‐ion mass spectrometry (SIMS) for submicron abrupt pn junctions (grown by molecular beam epitaxy) and Gaussian implants. The discrepancies between SR and SIMS are explained in terms of carrier spilling. From the comparison with a theoretical model, general trends can be adequately explained. In order to overcome the uncertainties imposed by the boundary conditions in this model, experimental diagrams are derived which can be used in routine analysis to assess the importance of carrier spilling effects in SR.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

1.54 μm room‐temperature luminescence of MeV erbium‐implanted silica glass

A. Polman, A. Lidgard, D. C. Jacobson, P. C. Becker, R. C. Kistler, G. E. Blonder, and J. M. Poate

Appl. Phys. Lett. 57, 2859 (1990); http://dx.doi.org/10.1063/1.104203 (3 pages) | Cited 25 times

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MeV erbium implantation doping of 10‐μm‐thick silica glass films on a Si substrate is studied with the aim of incorporating the rare‐earth dopant on an optically active site in the silica network. As‐implanted samples (3.5 MeV, 5×1015 Er ions/cm2) show a strong luminescent transition at a wavelength of 1.54 μm, even at room temperature, corresponding to an intra‐4f transition of Er3+. Thermal annealing at temperatures up to 900 °C increases the luminescence intensity by a factor of 2 to 3. For temperatures above 1000 °C the intensity decreases drastically as a result of Er precipitation. The lifetime of the excited state is in the order of 10 ms. Photoluminescence studies at 4.2 K are used to identify implantation‐induced damage.
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78.55.Hx Other solid inorganic materials
78.47.-p Spectroscopy of solid state dynamics
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