Hot-electron noise and diffusion in AlGaAs/GaAs

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Abstract
The electric field dependence of the microwave noise temperature and the diffusion coefficient are found to be significantly different for two sets of AlGaAs/GaAs structures with different spacer thickness and aluminium mole fraction. In the samples with a 'wide' quantum well (QW), one maximum of the diffusion coefficient is observed at fields below the threshold for the intervalley diffusion, but two maxima are characteristic of a 'narrow' QW with an intersubband gap wider than the KBTO. A microscopic explanation of the observed noise spectra of AlGaAs/GaAs is given and used to determine kinetic parameters of the heterostructures.