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The Growth of InAsSb/InAs/InPSb/InAs Mid-Infrared Emitters by Metal-Organic Chemical Vapor Deposition

Description: We report on the metal-organic chemical vapor deposition (MOCVD) of strained layer superlattices (SLSs) of InAsSb/InAs/InPSb/InAs as well as mid-infrared optically pumped lasers grown using a high speed rotating disk react,or (RDR). The devices contain AIAsSb cladding layers and strained, type I, InAsSb/InAs/InPSb/InAs strained layer superlattice (SLS) active regions. By changing the layer thickness and composition of the SLS, we have prepared structures with low temperature (<20K) photoluminescence wavelengths ranging from 3.4 to 4.8 pm. The optical properties of the InAsSb/InPSb superlattices revealed an anomalous low energy transition that can be assigned to an antimony-rich, interfacial layer in the superlattice. This low energy transition can be eliminated by introducing a 1.0 nm InAs layer between the InAsSb and InPSb layers in the superlattice. An InAsSb/InAs/lnPSbflnAs SLS laser was grown on an InAs substrate with AlAs{sub 0.16}Sb{sub 0.84} cladding layers. A lasing threshold and spectrally narrowed laser emission were seen from 80 through 250 K, the maximum temperature where lasing occurred. The temperature dependence of the SLS laser threshold is described by a characteristic temperature, T{sub 0} = 39 K, from 80 to 200 K.
Date: December 8, 1999
Creator: BIEFELD,ROBERT M.; PHILLIPS,J.D. & KURTZ,STEVEN R.
Partner: UNT Libraries Government Documents Department

GaAsSb/InGaAs type-II quantum wells for long-wavelength lasers on GaAs substrates

Description: The authors have investigated the properties of GaAsSb/InGaAs type-II bilayer quantum well structures grown by molecule beam epitaxy for use in long-wavelength lasers on GaAs substrates. Structures with layer, strains and thicknesses designed to be thermodynamically stable against dislocation formation exhibit room-temperature photoluminescence at wavelengths as long as 1.43 {mu}m. The photoluminescence emission wavelength is significantly affected by growth temperature and the sequence of layer growth (InGaAs/GaAsSb vs GaAsSb/InGaAs), suggesting that Sb and/or In segregation results in non-ideal interfaces under certain growth conditions. At low injection currents, double heterostructure lasers with GaAsSb/InGaAs bilayer quantum well active regions display electroluminescence at wavelengths comparable to those obtained in photoluminescence, but at higher currents the electroluminescence shifts to shorter wavelengths. Lasers have been obtained with threshold current densities as low as 120 A/cm{sup 2} at 1.17 {mu}m, and 2.1 kA/cm{sup 2} at 1.21 {mu}m.
Date: March 15, 2000
Creator: Klem, John F.; Spahn, Olga B.; Kurtz, Steven R.; Fritz, Ian J. & Choquette, Kent D.
Partner: UNT Libraries Government Documents Department

GaInNAs laser gain

Description: The optical gain spectra for GaInNAs/GaAs quantum wells are computed using a microscopic laser theory. From these spectra, the peak gain and carrier radiative decay rate as functions of carrier density are determined. These dependences allow the study of the lasing threshold current density of GaInNAs/GaAs quantum well structures.
Date: May 23, 2000
Creator: CHOW,WENG W.; JONES,ERIC D.; MODINE,NORMAND A.; KURTZ,STEVEN R. & ALLERMAN,ANDREW A.
Partner: UNT Libraries Government Documents Department

Minority carrier diffusion, defects, and localization in InGaAsN with 2% nitrogen

Description: Electron and hole transport in compensated, InGaAsN ({approx} 2% N) are examined through Hall mobility, photoconductivity, and solar cell photoresponse measurements. Short minority carrier diffusion lengths, photoconductive-response spectra, and doping dependent, thermally activated Hall mobilities reveal a broad distribution of localized states. At this stage of development, lateral carrier transport appears to be limited by large scale (>> mean free path) material inhomogeneities, not a random alloy-induced mobility edge.
Date: May 3, 2000
Creator: Kurtz, Steven R.; Allerman, Andrew A.; Seager, Carleton H.; Sieg, Robert M. & Jones, Eric D.
Partner: UNT Libraries Government Documents Department

The Growth of InGaAsN for High Efficiency Solar Cells by Metalorganic Chemical Vapor Deposition

Description: InGaAsN alloys are a promising material for increasing the efficiency of multi-junction solar cells now used for satellite power systems. However, the growth of these dilute N containing alloys has been challenging with further improvements in material quality needed before the solar cell higher efficiencies are realized. Nitrogen/V ratios exceeding 0.981 resulted in lower N incorporation and poor surface morphologies. The growth rate was found to depend on not only the total group III transport for a fixed N/V ratio but also on the N/V ratio. Carbon tetrachloride and dimethylzinc were effective for p-type doping. Disilane was not an effective n-type dopant while SiCl4 did result in n-type material but only a narrow range of electron concentrations (2-5e17cm{sup -3}) were achieved.
Date: September 16, 1999
Creator: ALLERMAN,ANDREW A.; BANKS,JAMES C.; GEE,JAMES M.; JONES,ERIC D. & KURTZ,STEVEN R.
Partner: UNT Libraries Government Documents Department

Photoluminescence-linewidth-derived exciton mass for InGaAsN alloys

Description: The authors report a measurement of the variation of the value of the linewidth of an excitonic transition in InGaAsN alloys (1 and 2% nitrogen) as a function of hydrostatic pressure using photoluminescence spectroscopy. The samples were grown by metal-organic chemical vapor deposition and the photoluminescence measurements were performed a 4K. The authors find that the value of the excitonic linewidth increases as a function of pressure until about 100 kbars after which it tends to saturate. This change in the excitonic linewidth is used to derive the pressure variation of the reduced mass of the exciton using a theoretical formalism which is based on the premise that the broadening of the excitonic transition is caused primarily by compositional fluctuations in a completely disordered alloy. The variation of the excitonic reduced mass thus derived is compared with that recently determined using a first-principles band structure calculation based on local density approximation.
Date: January 27, 2000
Creator: Jones, Eric D.; Allerman, Andrew A.; Kurtz, Steven R.; Modine, Normand A.; Bajaj, K. K.; Tozer, S. T. et al.
Partner: UNT Libraries Government Documents Department

Time-resolved photoluminescence studies of In{sub x}Ga{sub 1{minus}x}As{sub 1{minus}y}N{sub y}

Description: Time-resolved photoluminescence spectroscopy has been used to investigate carrier decay dynamics in a In{sub x}Ga{sub 1{minus}x}As{sub 1{minus}y}N{sub y} (x {approximately} 0.03, y {approximately} 0.01) epilayer grown on GaAs by metal organic chemical vapor deposition. Time-resolved photoluminescence (PL) measurements, performed for various excitation intensities and sample temperatures, indicate that the broad PL emission at low temperature is dominated by localized exciton recombination. Lifetimes in the range of 0.07--0.34 ns are measured; these photoluminescence lifetimes are significantly shorter than corresponding values obtained for GaAs. In particular, the authors observe an emission energy dependence of the decay lifetime at 10 K, whereby the lifetime decreases with increasing emission energy across the PL spectrum. This behavior is characteristic of a distribution of localized states, which arises from alloy fluctuations.
Date: January 27, 2000
Creator: MAIR,R.A.; LIN,J.Y.; JIANG,H.X.; JONES,ERIC D.; ALLERMAN,ANDREW A. & KURTZ,STEVEN R.
Partner: UNT Libraries Government Documents Department

Deep Levels in p- and n-type InGaAsN for High Efficiency Multi-Junction III-V Solar Cells

Description: Red Teaming is an advanced form of assessment that can be used to identify weaknesses in a variety of cyber systems. it is especially beneficial when the target system is still in development when designers can readily affect improvements. This paper discusses the red team analysis process and the author's experiences applying this process to five selected Information Technology Office (ITO) projects. Some detail of the overall methodology, summary results from the five projects, and lessons learned are contained within this paper.
Date: November 11, 1999
Creator: ALLERMAN,ANDREW A.; JONES,ERIC D.; KAPLAR,ROBERT J.; KURTZ,STEVEN R.; KWON,DAEWON & RINGEL,STEVEN A.
Partner: UNT Libraries Government Documents Department

InGaAsN: A Novel Material for High-Efficiency Solar Cells and Advanced Photonic Devices

Description: This report represents the completion of a 6 month Laboratory-Directed Research and Development (LDRD) program that focused on research and development of novel compound semiconductor, InGaAsN. This project seeks to rapidly assess the potential of InGaAsN for improved high-efficiency photovoltaic. Due to the short time scale, the project focused on quickly investigating the range of attainable compositions and bandgaps while identifying possible material limitations for photovoltaic devices. InGaAsN is a new semiconductor alloy system with the remarkable property that the inclusion of only 2% nitrogen reduces the bandgap by more than 30%. In order to help understand the physical origin of this extreme deviation from the typically observed nearly linear dependence of alloy properties on concentration, we have investigated the pressure dependence of the excited state energies using both experimental and theoretical methods. We report measurements of the low temperature photoluminescence energy of the material for pressures between ambient and 110 kbar. We describe a simple, density-functional-theory-based approach to calculating the pressure dependence of low lying excitation energies for low concentration alloys. The theoretically predicted pressure dependence of the bandgap is in excellent agreement with the experimental data. Based on the results of our calculations, we suggest an explanation for the strongly non-linear pressure dependence of the bandgap that, surprisingly, does not involve a nitrogen impurity band. Additionally, conduction-band mass measurements, measured by three different techniques, will be described and finally, the magnetoluminescence determined pressure coefficient for the conduction-band mass is measured. The design, growth by metal-organic chemical vapor deposition, and processing of an In{sub 0.07}Ga{sub 0.93}As{sub 0.98}N{sub 0.02} solar cell, with 1.0 eV bandgap, lattice matched to GaAs is described. The hole diffusion length in annealed, n-type InGaAsN is 0.6-0.8 pm, and solar cell internal quantum efficiencies >70% are obtained. Optical studies indicate that defects or impurities, from doping ...
Date: July 1, 1999
Creator: Allerman, Andrew A.; Follstaedt, David M.; Gee, James M.; Jones, Eric D.; Kurtz, Steven R. & Modine, Norman A.
Partner: UNT Libraries Government Documents Department

Effective masses for small nitrogen concentrations in InGaAsN alloys on GaAs

Description: The variation of the value of the linewidth of an excitonic transition in InGaAsN alloys (1% and 2% nitrogen) as a function of hydrostatic pressure using photoluminescence spectroscopy is studied at 4K. The excitonic linewidth increases as a function of pressure until about 100 kbar after which it tends to saturate. This pressure dependent excitonic linewidth is used to derive the pressure variation of the exciton reduced mass using a theoretical formalism based on the premise that the broadening of the excitonic transition is caused primarily by compositional fluctuations in a completely disordered alloy. The linewidth derived ambient pressure masses are compared and found to be in agreement with other mass measurements. The variation of this derived mass is compared with the results from a nearly first-principles approach in which calculations based on the local density approximation to the Kohn-Sham density functional theory are corrected using a small amount of experimental input.
Date: May 11, 2000
Creator: JONES,ERIC D.; ALLERMAN,ANDREW A.; KURTZ,STEVEN R.; FRITZ,IAN J.; MODINE,NORMAND A.; SIEG,ROBERT M. et al.
Partner: UNT Libraries Government Documents Department

Room temperature continuous wave InGaAsN quantum well vertical cavity lasers emitting at 1.3 um

Description: Selectively oxidized vertical cavity lasers emitting at 1294 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave at and above room temperature. The lasers employ two n-type Al{sub 0.94}Ga{sub 0.06}As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the optical cavity, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55 C. These lasers exhibit the longest wavelength reported to date for vertical cavity surface emitting lasers grown on GaAs substrates.
Date: June 5, 2000
Creator: CHOQUETTE,KENT D.; KLEM,JOHN F.; FISCHER,ARTHUR J.; SPAHN,OLGA B.; ALLERMAN,ANDREW A.; FRITZ,IAN J. et al.
Partner: UNT Libraries Government Documents Department