Effect of Intense Intersubband Optical Excitation on the Electron Distribution in GaAs/AlAs Quantum Wells

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Abstract
Hot electrons were generated in n-doped GaAs/AlAs multiple quantum wells by optical intersubband excitation and their energy distributions were studied at 10 K. By measuring photoluminescence (PL) spectra, the hot-electron temperatureTelwas quantitatively evaluated, taking into account such effects as the degenerate distribution of electrons, impurity-induced level broadening, and the distribution of holes. It was found that, when the intensityPof the excitation was 30 kW cm-2, i.e. a few percent of the onset intensity for absorption saturation,Telincreased from 10 K to 120 K while the lattice temperature remained unchanged. WhenPwas between 10 W cm-2and 30 kW cm-2, the rise ofTelwas well explained by the balance between the photon energy absorption and the energy loss due to the LO phonon emission inside the ground subband.