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The growth of InAsSb/InAsP strained-layer superlattices for use in infrared emitters

Description: We describe the metal-organic chemical vapor deposition growth of InAsSb/InAsP strained-layer superlattice (SLS) active regions for use in mid-infrared emitters. These SLSs were grown at 500{degrees}C, and 200 torr in a horizontal quartz reactor using TMIn, TESb, AsH{sub 3},and PH{sub 3}. By changing the layer thickness and composition we have prepared structures with low temperature ({le}20K) photoluminescence wavelengths ranging from 3.2 to 4.4 {mu}m. Excellent performance was observed for an SLS LED and both optically pumped and electrically injected SLS lasers. An optically pumped, double heterostructure laser emitted at 3.86 {mu}m with a maximum operating temperature of 240 K and a characteristic temperature of 33 K. We have also made electrically injected lasers and LEDs utilizing a GaAsSb/InAs semi-metal injection scheme. The semi-metal injected, broadband LED emitted at 4 {mu}m with 80 {mu}W of power at 300K and 200 mA average current. The InAsSb/InAsP SLS injection laser emitted at 3.6 gm at 120 K.
Date: June 1, 1997
Creator: Biefeld, R.M.; Allerman, A.A. & Kurtz, S.R.
Partner: UNT Libraries Government Documents Department

Spectral ellipsometry of GaSb and GaInAsSb: Experiment and modeling

Description: The optical constants {epsilon}(E)[={epsilon}{sub 1}(E)+i{epsilon}{sub 2}(E)] of single-crystal GaSb at 300K have been measured using spectral ellipsometry in the range of 0.3-5.3 eV. The {epsilon}(E) spectra displayed distinct structures associated with critical points (CPs) at E{sub 0} (direct gap), spin-orbit split E{sub 0}+{Delta}{sub 0} component, spin-orbit split (E{sub 1}, E{sub 1}+{Delta}{sub 1}) and (E{sub 0}{prime}, E{sub 0}{prime}+{Delta}{sub 0}{prime}) doublets, as well as E{sub 2}. The experimental data over the entire measured spectral range (after oxide removal) has been fit using the Holden model dielectric function based on the electronic energy-band structure near these CPs plus excitonic and band-to-band Coulomb enhancement effects at E{sub 0}, E{sub 0}+{Delta}{sub 0} and the E{sub 1}, E{sub 1}+{Delta}{sub 1} doublet. In addition to evaluating the energies of these various band-to-band CPs, information about the binding energy (R{sub 1}) of the two-dimensional exciton related to the E{sub 1}, E{sub 1}+{Delta}{sub 1} CPs was obtained. The value of R{sub 1} was in good agreement with effective mass/k{sup {rightharpoonup}}{center_dot}p{sup {rightharpoonup}} theory. The ability to evaluate R{sub 1} has important ramifications for recent first-principles band structure calculations which include exciton effects at E{sub 0}, E{sub 1}, and E{sub 2}. The experimental results were compared to other evaluations of the optical constants of GaSb.
Date: June 30, 1999
Creator: Charache, G.W.; Mu {tilde n}oz, M.; Wei, K.; Pollak, F.H. & Freeouf, J.L.
Partner: UNT Libraries Government Documents Department

Multi-staged, InAsSb mid-infrared lasers and light-emitting diodes, grown by MOCVD

Description: Due to lower nonradiative rates, mid-infrared (2-6 micron) lasers with strained, narrow bandgap, Sb-based active regions have the potential to operate at lower current density and higher temperature than competing devices. Superior performance may be achieved through the {open_quotes}band structure engineered{close_quotes} reduction of Auger recombination and the implementation of multi-stage (or {open_quotes}cascaded{close_quotes}) active regions. We describe the first lasers and LEDs utilizing strained InAsSb, multi-stage active regions. An (n)InAs / (p)GaAsSb semimetal layer is incorporated into each stage as an internal electron-hole source. To date, 2-stage LEDs and 2-stage lasers have been demonstrated. Our multi-stage devices were grown by MOCVD.
Date: September 1, 1997
Creator: Kurtz, S.R.; Allerman, A.A.; Biefeld, R.M. & Baucom, K.C.
Partner: UNT Libraries Government Documents Department

Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries: Part II. InP, InSb, InGaP and InGaAs

Description: A parametric study of Inductively Coupled Plasma etching of InP, InSb, InGaP and InGaAs has been carried out in IC1/Ar and IBr/Ar chemistries. Etch rates in excess of 3.1 prrdmin for InP, 3.6 prnh-nin for InSb, 2.3 pm/min for InGaP and 2.2 ~rrdmin for InGaAs were obtained in IBr/Ar plasmas. The ICP etching of In-based materials showed a general tendency: the etch rates increased substantially with increasing the ICP source power and rf chuck power in both chemistries, while they decreased with increasing chamber pressure. The IBr/Ar chemistry typically showed higher etch rates than IC1/Ar, but the etched surface mophologies were fairly poor for both chemistries.
Date: November 23, 1998
Creator: Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Hobson, W.S.; Jung, K.B. et al.
Partner: UNT Libraries Government Documents Department

Auger and Radiative Recombination Coefficients in 0.55 eV InGaAsSb

Description: A radio-frequency (RF) photoreflectance technique, which senses changes in sample conductivity as carriers recombine following excitation by a laser pulse, has been used to measure the recombination parameters in 0.55 eV InGaAsSb lattice matched to GaSb. Doubly-capped lifetime structures with variable active layer thicknesses are used to extract the surface recombination velocity (SRV), while analysis of the samples with different doping concentrations is used to obtain Auger (C) and radiative (B) recombination parameters. Parameter extraction for the samples evaluated gives C = 1 {+-} 0.4 x 10{sup -28} cm{sup 6}/s and B = 3 {+-} 1.5 x 10{sup -11} cm{sup 3}/s for 0.55 eV InGaAsSb lattice matched to GaSb. The Auger and radiative recombination coefficients obtained from high-level injection decay times in low doping concentration samples show very good agreement with values obtained from low-level injection conditions.
Date: August 4, 2004
Creator: Wang, CA & Nichols, G
Partner: UNT Libraries Government Documents Department

The optimization of interfaces in InAsSb/InGaAs strained-layer superlattices grown by metal-organic chemical vapor deposition

Description: We have prepared InAsSb/InGaAs strained-layer superlattice (SLS) semiconductors by metal-organic chemical vapor deposition (MOCVD) under a variety of conditions. Presence of an InGaAsSb interface layer is indicated by x-ray diffraction patterns. Optimized growth conditions involved the use of low pressure, short purge times, and no reactant flow during the purges. MOCVD was used to prepare an optically pumped, single heterostructure InAsSb/InGaAs SLS/InPSb laser which emitted at 3.9 {mu}m with a maximum operating temperature of approximately 100 K.
Date: December 31, 1993
Creator: Biefeld, R. M.; Baucom, K. C. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department

Measurements of High-Field THz Induced Photocurrents in Semiconductors

Description: THz pulses have provided a useful tool for probing, with time resolution, the free carriers in a system. The development of methods to produce intense THz radiation has been slow since spectroscopists and condensed matter physicists first began probing materials with THz pulses. We have developed a method for producing intense ultra-short THz pulses, which have full width half maximum of 300 fs - approximately a half cycle of THz radiation. These intense half cycle pulses (HCPs) allow us to use THz radiation not only as a probe of the free carriers in a system but also as a source of excitation to alter a system in some way. In particular, HPCs perturb free carriers considerably in short time scales but show minimal effect to individual free carriers over long time. By exposing the semiconductor indium antimonide (InSb) to our intense THz HCP radiation, we have observed non-linear optical effects which suggest the generation of new free carriers by below band-gap THz photons. This generation of free carriers appears to be caused by an avalanche multiplication process, which should amplify the number of free carriers already in the system and then induce a current in the timescale of our THz pulse. This amplification on such a short timescale suggests the possibility of an ultra-fast detector of weak above band-gap radiation. We constructed a device which detects these currents by painting an electrode structure on the surface of the semiconductor. The currents induced across the electrodes by this avalanche multiplication process were measured and compared with other measurements of this non-linear optical process. We successfully measured THz induced currents in InSb, which indicate promise towards the development of an ultra-fast detector, and we gain insight into a possible physical explanation of the THz induced free carriers we observe in InSb.
Date: November 7, 2007
Creator: Wiczer, Michael & /Illinois U., Urbana
Partner: UNT Libraries Government Documents Department

Czochralski growth of gallium indium antimonide alloy crystals

Description: Attempts were made to grow alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb by the conventional Czochralski process. A transparent furnace was used, with hydrogen purging through the chamber during crystal growth. Single crystal seeds up to about 2 to 5 mole% InSb were grown from seeds of 1 to 2 mole% InSb, which were grown from essentially pure GaSb seeds of the [111] direction. Single crystals were grown with InSb rising from about 2 to 6 mole% at the seed ends to about 14 to 23 mole% InSb at the finish ends. A floating-crucible technique that had been effective in reducing segregation in doped crystals, was used to reduce segregation in Czochralski growth of alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb. Crystals close to the targeted composition of 1 mole% InSb were grown. However, difficulties were encountered in reaching higher targeted InSb concentrations. Crystals about 2 mole% were grown when 4 mole% was targeted. It was observed that mixing occurred between the melts rendering the compositions of the melts; and, hence, the resultant crystal unpredictable. The higher density of the growth melt than that of the replenishing melt could have triggered thermosolutal convection to cause such mixing. It was also observed that the floating crucible stuck to the outer crucible when the liquidus temperature of the replenishing melt was significantly higher than that of the growth melt. The homogeneous Ga{sub 1{minus}x}In{sub x}Sb single crystals were grown successfully by a pressure-differential technique. By separating a quartz tube into an upper chamber for crystal growth and a lower chamber for replenishing. The melts were connected by a capillary tube to suppress mixing between them. A constant pressure differential was maintained between the chambers to keep the growth melt up in the growth chamber. The method was first tested with a low temperature alloy Bi{sub ...
Date: February 1, 1998
Creator: Tsaur, S.C.
Partner: UNT Libraries Government Documents Department

Optical constants of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} lattice-matched to GaSb(001): Experiment and modeling

Description: The optical constants {epsilon}(E)[={epsilon}{sub 1}(E)+i{epsilon}{sub 2}(E)] of two epitaxial layers of GaInAsSb/GaSb have been measured at 300 K using spectral ellipsometry in the range of 0.35--5.3 eV. The {epsilon}(E) spectra displayed distinct structures associated with critical points (CPs) at E{sub 0} (direct gap), spin-orbit split E{sub 0}+{Delta}{sub 0} component, spin-orbit split (E{sub 1}, E{sub 1}+{Delta}{sub 1}) and (E{sub 0}{prime}, E{sub 0}{prime}+{Delta}{sub 0}{prime}) doublets, as well as E{sub 2}. The experimental data over the entire measured spectral range (after oxide removal) has been fit using the Holder model dielectric function [Phys.Rev.B 56, 4037 (1997)] based on the electronic energy-band structure near these CPs plus excitonic and band-to-band Coulomb enhancement effects at E{sub 0.}, E{sub 0}+{Delta}{sub 0} and the E{sub 1}, E{sub 1}+{Delta}{sub 1} doublet. In addition to evaluating the energies of these various band-to-band CPs, information about the binding energy (R{sub 1}) of the two-dimensional exciton related to the E{sub 1}, E{sub 1}+{Delta}{sub 1} CPs was obtained. The value of R{sub 1} was in good agreement with effective mass/k{sup {rightharpoonup}}{center_dot}p{sup {rightharpoonup}} theory. The ability to evaluate R{sub 1} has important ramifications for recent first-principles band structure calculations which include exciton effects at E{sub 0}, E{sub 1}, and E{sub 2} [M.Rohlfing and S.G.Louie, Phys.Rev.Lett. 81, 2312 (1998) and S. Albrecht et al., Phys.Rev.Lett. 80, 4510 (1998)]. The experimental absorption coefficients in the region of E{sub 0} were in good agreement with values obtained from a linear interpolation of the end point materials. The experimental results were compared to a recent evaluation and fitting (Holden model) of the optical constants of GaSb.
Date: June 1999
Creator: Charache, G. W.; Muñoz, M.; Wei, K.; Pollak, F. H.; Freeouf, J. L. & Wang, C. A.
Partner: UNT Libraries Government Documents Department

Bulk single crystal ternary substrates for a thermophotovoltaic energy conversion system

Description: A thermophotovoltaic energy conversion device and a method for making the device are disclosed. The device includes a substrate formed from a bulk single crystal material having a bandgap (E{sub g}) of 0.4 eV < E{sub g} < 0.7 eV and an emitter fabricated on the substrate formed from one of a p-type and an n-type material. Another thermophotovoltaic energy conversion device includes a host substrate formed from a bulk single crystal material and lattice-matched ternary or quaternary III-V semiconductor active layers.
Date: December 31, 1996
Creator: Charache, G.W.; Baldasaro, P.F. & Nichols, G.J.
Partner: UNT Libraries Government Documents Department

Growth and Characterization of Quantum Dots and Quantum Dots Devices

Description: Quantum dot nanostructures were investigated experimentally and theoretically for potential applications for optoelectronic devices. We have developed the foundation to produce state-of-the-art compound semiconductor nanostructures in a variety of materials: In(AsSb) on GaAs, GaSb on GaAs, and In(AsSb) on GaSb. These materials cover a range of energies from 1.2 to 0.7 eV. We have observed a surfactant effect in InAsSb nanostructure growth. Our theoretical efforts have developed techniques to look at the optical effects induced by many-body Coulombic interactions of carriers in active regions composed of quantum dot nanostructures. Significant deviations of the optical properties from those predicted by the ''atom-like'' quantum dot picture were discovered. Some of these deviations, in particular, those relating to the real part of the optical susceptibility, have since been observed in experiments.
Date: April 1, 2003
Creator: CEDERBERG, JEFFREY G.; BIEFELD, ROBERT M.; SCHNEIDER, H.C. & CHOW, WENG W.
Partner: UNT Libraries Government Documents Department

Uncooled IR photon detection using MEMS micro-structures

Description: Generation of free carriers in a semiconductor gives rise to mechanical stress. Photo-induced stress phenomena in MEMS micro-structures can be used in the room temperature detection of infrared photons. Choice of the appropriate semiconductor material for the MEMS micro-structures determines the cutoff wavelength of the uncooled infrared photon detector. The authors have measured the deflection of silicon and indium antimonide micro-structures resulting from a photo-induced stress. The excess charge carriers responsible for the photo-induced stress were produced via photon irradiation from both a diode laser and a black body source. In the case of Si, the photo-induced stress is of opposite direction and about four times larger than the thermal stress. For indium antimonide the direction of stress is the same as due to thermal effects. The photo-induced stress can be distinguished from the thermal stress based on the cut-off wavelength, response speed, and perhaps the direction of the microstructure deflection.
Date: August 1, 1998
Creator: Datskos, P.G. & Rajic, S.
Partner: UNT Libraries Government Documents Department

Bridgman growth and characterization of bulk single crystals of Ga{sub 1{minus}x}In{sub x}Sb for thermophotovoltaic applications

Description: Thermophotovoltaic generation of electricity is attracting renewed attention due to recent advances in low bandgap (0.5--0.7 eV) III-V semiconductors. The use of mixed pseudo-binary compounds allows for the tailoring of the lattice parameter and the bandgap of the material. Conventional deposition techniques (i.e., epitaxy) for producing such ternary or quaternary materials are typically slow and expensive. Production of bulk single crystals of ternary materials, for example Ga{sub 1{minus}x}In{sub x}Sb, is expected to dramatically reduce such material costs. Bulk single crystals of Ga{sub 1{minus}x}In{sub x}Sb have been prepared using a Bridgman technique in a two-zone furnace. These crystals are 19 mm in diameter by approximately 50 mm long and were produced using seeds of the same diameter. The effects of growth rate and starting materials on the composition and quality of these crystals will be discussed and compared with other attempts to produce single crystals of this material.
Date: December 1, 1997
Creator: Boyer, J.R. & Haines, W.T.
Partner: UNT Libraries Government Documents Department

Bulk crystal growth of antimonide based III-V compounds for thermophotovoltaics applications

Description: In this paper, the bulk growth of crack-free GaInSb and single phase GaInAsSb alloys are presented. A new class of III-V quasi-binary [A{sub III}B{sub V}]{sub 12{minus}x}[C{sub III}D{sub V}]{sub x} semiconductor alloys has been synthesized and bulk crystals grown from the melt for the first time. The present investigation is focused on the quasi-binary alloy (GaSb){sub 1{minus}x}(InAs){sub x} (0 < x < 0.05) due to its importance for thermophotovoltaic applications. The structural properties of this melt-grown quasi-binary alloy are found to be significantly different from the conventional quaternary compound Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} with composition x = y. Synthesis and growth procedures are discussed. For the growth of ternary alloys, it was demonstrated that forced convection or mixing in the melt during directional solidification of In{sub x}Ga{sub 1{minus}x}Sb (0 < x < 0.1) significantly reduces cracks in the crystals.
Date: October 1, 1998
Creator: Dutta, P.S.; Ostrogorsky, A.G. & Gutmann, R.J.
Partner: UNT Libraries Government Documents Department

Novel mid-infrared lasers with compressively strained InAsSb active regions

Description: Mid-infrared lasers grown by MOCVD with AlAsSb claddings and strained InAsSb active regions are reported. A 3.8--3.9 {micro}m injection laser with a pseudomorphic InAsSb multiple quantum well active region lased at 210 K under pulsed operation. A semi-metal layer acts as an internal electron source for the injection laser. An optically pumped laser with an InAsSb/InAsP strained-layer superlattice active region was demonstrated at 3.7 {micro}m, 240 K.
Date: February 1, 1997
Creator: Kurtz, S.R.; Biefeld, R.M. & Allerman, A.A.
Partner: UNT Libraries Government Documents Department

Growth and characterization of In{sub 0.2}Ga{sub 0.8}Sb device structures using metalorganic vapor phase epitaxy

Description: In{sub 0.2}Ga{sub 0.8}Sb epitaxial layers and thermophotovoltaic (TPV) device structures have been grown on GaSb and GaAs substrates by metalorganic vapor phase epitaxy (MOVPE). Control of the n-type doping up to 1 {times} 10{sup 18} cm{sup {minus}3} was achieved using diethyltellurium (DETE) as the dopant source. A Hall mobility of greater than 8,000 cm{sup 2}/Vs at 77 K was obtained for a 3 {times} 10{sup 17} cm{sup {minus}3} doped In{sub 0.2}Ga{sub 0.8}Sb layer grown on high-resistivity GaSb substrate. The In{sub 0.2}Ga{sub 0.8}Sb epilayers directly grown on GaSb substrates were tilted with respect to the substrates, with the amount of tilt increasing with the layer thickness. Transmission electron microscopy (TEM) studies of the layers showed the presence of dislocation networks across the epilayers parallel to the interface at different distances from the interface, but the layers above this dislocation network were virtually free of dislocations. A strong correlation between epilayer tilt and TPV device properties was found, with layers having more tilt providing better devices. The results suggest that the dislocations moving parallel to the interface cause lattice tilt, and control of this layer tilt may enable the fabrication of better quality device structures.
Date: May 1, 1997
Creator: Ehsani, H.; Bhat, I.; Hitchcock, C.; Gutmann, R.; Charache, G. & Freeman, M.
Partner: UNT Libraries Government Documents Department

Silicon as the P-type dopant in GaSb and Ga{sub 0.8}In{sub 0.2}Sb grown by metalorganic vapor phase epitaxy

Description: P-type GaSb and Ga{sub 0.8}In{sub 0.2}Sb layers have been grown on GaSb and GaAs substrates by metalorganic vapor phase epitaxy (MOVPE) using silane as the doping precursor. Hall measurements show that the concentration and mobility of holes in GaSb and Ga{sub 0.8}In{sub 0.2}Sb are higher when the layers are grown on GaSb substrates than when grown on GaAs substrates. Secondary ion mass spectroscopy (SIMS) results show that the incorporation of Si is higher when GaSb substrates are used. The compensation of Si acceptors is negligible in GaSb, but is as high as 25% in Ga{sub 0.8}In{sub 0.2}Sb.
Date: June 1, 1998
Creator: Ehsani, H.; Bhat, I.; Hitchcock, C. Gutmann, R.J.; Charache, G. & Freeman, M.
Partner: UNT Libraries Government Documents Department

Tellurium doping of Ga{sub 0.8}In{sub 0.2}Sb layers grown by metalorganic vapor phase epitaxy

Description: N-type Ga{sub 0.8}In{sub 0.2}Sb epitaxial layers have been grown on GaSb and GaAs substrates by metalorganic vapor phase epitaxy (MOVPE) using diethyltelluride (DETe) as the dopant source. The incorporation efficiency of Te in Ga{sub 0.8}In{sub 0.2}Sb and the electron mobility were found to be higher with GaSb substrates compared to using GaAs substrates. The electron concentration increased from 5 {times} 10{sup 16} cm{sup {minus}3} to 1.5 {times} 10{sup 18} cm{sup {minus}3} as the Te concentration was increased from 1 {times} 10{sup 17} cm{sup {minus}3} to 5 {times} 10{sup 18} cm{sup {minus}3}. As the Te concentration was increased further, the electron concentration decreased, with only about 1% of the Te electrically active at a Te concentration of 2 {times} 10{sup 20} cm{sup {minus}3}.
Date: June 1, 1998
Creator: Ehsani, H.; Bhat, I.; Hitchcock, C.; Gutmann, R.J.; Charache, G. & Freeman, M.
Partner: UNT Libraries Government Documents Department

Bulk growth of GaSb and Ga{sub 1{minus}x}In{sub x}Sb

Description: GaSb and InGaSb have been demonstrated to be suitable choices for high efficiency thermophotovoltaic (TPV) cells. Synthesis and growth of bulk GaSb single crystals and GaInSb polycrystals have been carried out by the vertical Bridgman technique, with a baffle immersed in the melt and by complete encapsulation of the melt by low melting temperature alkali halides or oxides. The critical roles of the baffle and the encapsulation are discussed. Efforts in obtaining device grade GaSb with superior structural and electrical properties and compositionally homogeneous GaInSb are described, emphasizing the key steps in the growth cycle developed to obtain good crystalline quality.
Date: May 1, 1997
Creator: Dutta, P.S.; Ostrogorsky, A.G. & Gutmann, R.J.
Partner: UNT Libraries Government Documents Department

Extending the cutoff wavelength of lattice-matched GaInAsSb/GaSb thermophotovoltaics devices

Description: This paper reports the growth, materials characterization, and device performance of lattice-matched GaInAsSb/GaSb thermophotovoltaic (TPV) devices with cutoff wavelength as long as 2.5 {micro}m. GaInAsSb epilayers were grown lattice matched to GaSb substrates by organometallic vapor phase epitaxy (OMVPE) using all organometallic precursors including triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony with diethyltellurium and dimethylzinc as the n- and p-type dopants, respectively. The growth temperature was 525 C. Although these alloys are metastable, a mirror-like surface morphology and room temperature photoluminescence (PL) are obtained for alloys with PL peak emission at room temperature as long as 2.5 {micro}m. In general, however, a trend of decreasing material quality is observed as the wavelength increases. Both the surface roughness and PL full width at half-maximum increase with wavelength. In spite of the dependence of material quality on PL peak emission wavelength, the internal quantum efficiency of TPV devices with cutoff wavelengths of 2.3 to 2.5 {micro}m is as high as 86%.
Date: October 1, 1998
Creator: Wang, C.A.; Choi, H.K.; Oakley, D.C. & Charache, G.W.
Partner: UNT Libraries Government Documents Department

In-situ monitoring of GaSb, GaInAsSb, and AlGaAsSb

Description: Suitability of silicon photodiode detector arrays for monitoring the spectral reflectance during epitaxial growths of GaSb, AlGaAsSb, and GaInAsSb, which have cutoff wavelengths of 1.7, 1.2, and 2.3 {micro}m, respectively, is demonstrated. These alloys were grown lattice matched to GaSb in a vertical rotating-disk reactor, which was modified to accommodate near normal reflectance without affecting epilayer uniformity. By using a virtual interface model, the growth rate and complex refractive index at the growth temperature are extracted for these alloys over the 600 to 950 nm spectral range. Excellent agreement is obtained between the extracted growth rate and that determined by ex-situ measurement. Optical constants are compared to theoretical predictions based on an existing dielectric function model for these materials. Furthermore, quantitative analysis of the entire reflectance spectrum yields valuable information on the approximate thickness of overlayers on the pregrowth substrate.
Date: June 1, 1998
Creator: Vineis, C.J.; Wang, C.A.; Jensen, K.F. & Breiland, W.G.
Partner: UNT Libraries Government Documents Department

Interfaces in InAsSb/InGaAs strained-layer superlattices grown by MOCVD for use in infrared emitters

Description: The authors have prepared InAsSb/InGaAs strained-layer superlattices (SLSs) using metal-organic chemical vapor deposition (MOCVD). X-ray diffraction was used to determine lattice matching as well as composition and structure of the SLS`s. The presence of an InGaAsSb interface layer was indicated by x-ray diffraction for samples grown under non-optimized conditions. Interfacial layers were also identified with transmission electron microscopy (TEM). Two types of interfaces were observed by TEM. The different contrasts observed by TEM could be due to a difference in composition at the interfaces. The width of the x-ray peaks can be explained by a variation of the layer thickness.
Date: February 1, 1995
Creator: Biefeld, R.M.; Follstaedt, D.M.; Kurtz, S.R. & Baucom, K.C.
Partner: UNT Libraries Government Documents Department