Photoluminescence and tunneling in Gallium arsenide/aluminum gallium arsenide single quantum wells

This thesis presents the growth, processing, and optical and electronic measurement of two sets of GaAs/Al{dollar}sb{lcub}x{rcub}{dollar}Ga{dollar}sb{lcub}1-x{rcub}{dollar}As single quantum well, double barrier heterostructures. One set is designed for resonant and phonon-assisted tunneling measurements, and a second set is designed with GaAs quantum well widths near the type-I/type-II crossover. The molecular beam epitaxial growth procedures utilized to grow these structures are presented, including techniques for obtaining desired Al mole fractions by varying source temperatures.; The effect of barrier height on tunneling currents has been studied for a set of asymmetric GaAs/Al{dollar}sb{lcub}x{rcub}{dollar}Ga{dollar}sb{lcub}1-x{rcub}{dollar}As double barrier structures by varying the barrier Al mole fraction in the range, {dollar}0.2le xle0.8.{dollar} The barrier widths of each sample were scaled so that barrier transmission coefficients for different samples should be approximately equivalent at the first resonant tunneling peak. Current-voltage measurements show large phonon-assisted tunneling features, and resonant tunneling current levels that were roughly normalized as predicted by a simple expression for {dollar}Gamma{dollar}-point tunneling.; Another set of GaAs/AlAs single quantum well structures designed with well thickness near the type-I/type-II crossover show distinctive photoluminescence peaks corresponding to both type-I and type-II recombination. Type-I transitions correspond to direct recombination of {dollar}Gamma{dollar} electrons and {dollar}Gamma{dollar} holes, both in the GaAs well, while type-II transitions correspond to indirect recombination of X electrons in the AlAs barrier with {dollar}Gamma{dollar} holes in the GaAs well. Photoluminescence measurements were made as a function of applied electric field, incident excitation intensity, and temperature ranging from 1.4-300 K. Current-voltage measurements were also made, and structures were grown with both n-i-n and p-i-n cladding in order to more fully investigate the electric field dependence of these type-I and type-II transitions. {dollar}Gamma{dollar}-X mixing mechanisms were studied and from n-i-n samples, a {dollar}Gamma{dollar}-X mixing energy of a few meV was measured, consistent with values measured in superlattices of comparable well thickness. In the p-i-n sample, three distinct luminescence peaks from recombination in the well and in each barrier were observed. The availability of electrons in the conduction band states is explained by photoexcitation and electronic injection.