Native Oxides on Aluminum-Bearing Iii-V Semiconductors: Material Characterization and Application to Quantum Well Heterostructure Lasers

Sugg, Alan Richard

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Description

Title

Native Oxides on Aluminum-Bearing Iii-V Semiconductors: Material Characterization and Application to Quantum Well Heterostructure Lasers

Author(s)

Sugg, Alan Richard

Issue Date

1993

Doctoral Committee Chair(s)

Holonyak, N., Jr.,

Department of Study

Electrical Engineering

Discipline

Electrical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(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.

Graduation Semester

1993

Type of Resource

text

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