砷化鎵中熱載子的弛緩程序

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-. (a) Schematic of cw spectroscopy of ultrafast processes in GaAs. The vertical arrow on the left shows excitation of electrons from the light-hole valence band to the conduction band by a cw dye laser. The steady-state distribution of electrons consists of a series of peaks, spaced by the LO-phonon energy. Individual electrons take only a few hundred femtoseconds to relax through this cascade. The luminescence transitions are indicated as vertical arrows. For clarity only processes involving the light-hole band are shown in (a). In the experiment, equivalent processes involving the heavy-hole band are superimposed. (b) This figure shows hot-electron luminescence near point r to scale. The steady-state distribution of electrons excited both from the heavy-and the light-hole bheavy-ands are shown to scale. The inset on the right-hand side shows the corresponding luminescence spectrum on a logarithmic scale. (%*R: G. Faso1 at al.. 1 990t7])I\

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HZ. Time resolved transmittance spectra (log,,, transmission) of GaAs at 15 K for different time delays between the pump and probe pulses. The dotted-line curve represents the transmission at t=O psec (just before the excitation). The dashed curve corresponds to a delay of 4.2 psec, a time significantly longer than the pump-pulse duration (0.5 psec FWHM). The pump-pulse spectrum is displayed in the lower part of the figure.

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AI,,,Ga,,,As/G~As: Be,T=lOK N,=1.0x10'8cm~3 3 's,, cd 'y ho,,=1,797eV Unrelaxed \ /,peak r.- ,,,e A(J),? C ‘.<_/ *,, E! '~: ,_',Tf“ 2_C _J ;_l\+'LJ', - .s-_.. 1.65 1.80

Photon Energy (eV)

AlO,,,Ga,,,,As/GaAs f3#@*N%#S%i %!%zz?MFfi~Y~~Et PL 3% ; S$@Sw&E& 690nm 0 ff$ unrelaxed peak &P&Rl$.8 EzQ@~X3 o (a) AI,,,Ga,,,As/GaAs:Be,T=lOK N,=l.0x10'Bcm~3,h~~X=l.797eV nzD= 1x109cm~2 (b) n20 = 2x10'0cm~Z -- .x_-._._^_ ---.__ -._ .._ - ‘I -_ (‘I n = 6x10’0cm’2_xl “..._ -_-..._p ---- _.__ '. '.\ --.._, 5-.-c.. j75 1 750

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experiment data‘ _ fitting curve

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