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 Title: Native Oxides on Aluminum-Bearing Iii-V Semiconductors: Material Characterization and Application to Quantum Well Heterostructure Lasers Author(s): Sugg, Alan Richard Doctoral Committee Chair(s): Holonyak, N., Jr., Department / Program: Electrical Engineering Discipline: Electrical Engineering Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Engineering, Electronics and Electrical Physics, Electricity and Magnetism Physics, Condensed Matter Engineering, Materials Science Abstract: Data are presented on the comparison of the chemical stability of oxides of AlAs-GaAs heterostructures formed via atmospheric hydrolysis and by native oxidation at 400$\sp\circ$C for 3 h in a N$\sb2$ + H$\sb2$O vapor. Data indicate that atmospheric hydrolysis involves a chemical reaction that is destructive to the semiconductor material, while native oxidation produces chemically stable compounds that do not attack the semiconductor.The effects of low-temperature annealing, both with and without excess As, on the native oxides of Al$\sb{0.8}$Ga$\sb{0.2}$As are also studied. The samples are analyzed with transmission electron microscopy (TEM), Auger electron spectroscopy (AES), ellipsometry ($\lambda$ = 6328 A), and SIMS. These data show the as-oxidized (425$\sp\circ$C, 40 min) material to be a fine-grained amorphous oxide comprised of moderate temperature phases of Al$\sb2$O$\sb3,$ $\eta,$ $\gamma,$ $\delta,$ or $\chi$ or AlO(OH). The AES data indicate that the Al is oxidized while the Ga remains unoxidized. The native oxide is As-depleted and contains $\sim$50% oxygen. The index of refraction of the oxide is 1.63.After being annealed in an evacuated quartz ampoule at 540$\sp\circ$C for 4 h with no excess As, the composition of the oxide remains unchanged, but ellipsometer measurements indicate the creation of a secondary interface region $\sim$550 A thick with an index of refraction of $\sim$2.93.In contrast, upon annealing the oxide at the same time and temperature with excess As the oxide changes to a finer-grained amorphous material than the as-oxidized crystal. Electron diffraction data show that the oxide has undergone a change in phase or composition as a result of annealing with an excess As overpressure. Also, a secondary interface region $\sim$300 A thick has developed with an index of refraction of 2.78.Native-oxide-embedded Al$\sb{\rm y }$Ga$\sb{\rm 1-y}$As-GaAs-In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As quantum well heterostructures (QWH) have been fabricated and operated as photopumped lasers continuously (cw) at both 77 K and 300 K. In these structures the GaAs-In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As active region of the QWH is sandwiched between native oxide grown laterally across the entire width of an etched mesa stripe. A comparison of lasing threshold current densities shows no apparent degradation of the oxide-embedded samples relative to the as-grown QWHs.Data are also presented on Al$\sb{\rm y}$Ga$\sb{\rm 1-y}$As-GaAs-In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As QWH laser diodes grown on n-type substrates employing a reverse-biased p+/n+ tunnel junction. The 10 $\mu$m-wide stripe devices are defined using the native oxide (425$\sp\circ$C, 15 min) and operate cw at 300 K with a lasing threshold current of 37 mA (cavity length $\sim$375 $\mu$m). The series resistance is $\sim$10 $\Omega$ at 50 mA. Issue Date: 1993 Type: Text Description: 109 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993. URI: http://hdl.handle.net/2142/72006 Other Identifier(s): (UMI)AAI9329171 Date Available in IDEALS: 2014-12-16 Date Deposited: 1993
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