HOT-ELECTRON NOISE AND DIFFUSION IN ALGAAS GAAS/

The electric field dependence of the microwave noise temperature and t he diffusion coefficient are found to be significantly different for t wo 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 belo w the threshold for the intervalley diffusion, but two maxima are char acteristic of a 'narrow' QW with an intersubband gap wider than the k( B)T0. A microscopic explanation of the observed noise spectra of AlGaA s//GaAs is given and used to determine kinetic parameters of the heter ostructures.