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(a) Midinfrared intersubband transmission spectra of the sample containing 31 Å wide carbon modulation-doped GaAs QWs with digital alloy barriers. The spectra for -polarized (black line) and -polarized (gray line) light are shown for measurements at 17 K. The inset shows the experimental multipass waveguide geometry. (b) Absorption coefficient for the 31 Å QW sample at 17 K (black line) and 300 K (gray line).
(a) Comparison of the experimental (circles) heavy-to-heavy hole transition energy for four different QW widths with the calculations of the six-band model assuming the barriers consisting of homogeneous alloy (triangles), and simulating the full band structure of the digital alloy (squares). The calculated points were offset horizontally by for clarity. The lines are linear fits through the data to guide the eye. The vertical bars through the experimental data points show the experimental FWHM. For the calculated data, the error bars equal to 10% of the peak transition energies. (b) Full valence-band structure including the detailed structure of the digital alloy barriers for a 31 Å QW doped at the level of . The heavy-to-heavy hole transition is indicated with a dark gray arrow, while the most likely heavy-to-light hole transition is indicated by the light-gray arrow.
Experimental heavy-to-heavy hole transition energies and FWHM of the -polarized absorption spectra for the corresponding QW widths.
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