Magnetic-field-induced nonthermal occupation of higher subbands in a three-barrier tunneling structure

When injected electrons in a quantum well first experience an intersubband relaxation process before their escaping by tunneling through a double-barrier structure behind, the magnetic suppression of intersubband LO or LA phonon scattering can give rise to a noticeable nonthermal occupation in higher-lying subbands. That is clearly verified by the relative intensity ratio of the interband photoluminescence spectra for E-2-HH1 and E-1-HH1 transitions. The observed phenomenon may provide an effective method for controlling intersubband scattering rate, a central issue in so-called quantum cascade lasers, and facilitating the population inversion between subbands in quantum wells.

Occupation modulation of higher subbands in a three-barrier tunnelling structure with a magnetic field

We verify that the magnetic suppression of intersubband LO or LA phonon scattering can give rise to a noticeable nonthermal occupation in higher-lying subbands. This is clearly determined by the relative intensity ratio of the interband photoluminescence spectra for the E-2 - HH1 and E-1 - HH1 transitions. The observed phenomenon may provide an effective method to control the intersubband scattering rate, which is a key factor of the so-called quantum cascade lasers. This is helpful for the population inversion between both the subbands in quantum wells.

Effect of partial site occupation on the magnetic properties of Nd2Fe17-xSix by supercell calculation

The magnetic properties of the Nd2Fe17-xSix intermetallic compounds are studied by means of spin-polarized supercell calculations in which the selected sites of substitution are close to the situations in real samples. It is shown that the average Fe moment increases with x and saturates near x = 3. This correlates quite well with the experimental dependence of Te on x. The difference between supercell and unit cell calculations are pointed out and the influence of Si atoms on the density of states of the nearby Fe atoms is emphasized. (C) 1997 American Institute of Physics.