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Figure 52. Optical absorption spectra (in units of W0), as a function of the hw — sg, for valence to donor transitions in infinite GaAs-(Ga,Al)As quantum dots of different radii. r0 = 3000 A (a), r0 = 1000 A (full curve), and r0 = 500 A (dashed curve) (b). and e!1 (e2 and e2) correspond, respectively, to the onset of transitions from the first valence subband to the lower (upper) edge of the impurity band. Reprinted with permission from [205], J. L. Marín et al., in "Handbook of Advanced Electronic and Photonic Materials and Devices" (H. S. Nalwa, Ed.). Academic Press, San Diego, 2001. © 2001, Academic Press.

Figure 52. Optical absorption spectra (in units of W0), as a function of the hw — sg, for valence to donor transitions in infinite GaAs-(Ga,Al)As quantum dots of different radii. r0 = 3000 A (a), r0 = 1000 A (full curve), and r0 = 500 A (dashed curve) (b). and e!1 (e2 and e2) correspond, respectively, to the onset of transitions from the first valence subband to the lower (upper) edge of the impurity band. Reprinted with permission from [205], J. L. Marín et al., in "Handbook of Advanced Electronic and Photonic Materials and Devices" (H. S. Nalwa, Ed.). Academic Press, San Diego, 2001. © 2001, Academic Press.

is a smooth function which exhibits a well-defined peak at the binding energy associated with on-edge donors. When the radius is very large, the structure of the smax Van Hove-like singularity is clearly a peak associated with on-center donors, which corresponds to the bulk limit. For quantum dots of r0 > 1000 A it is observed that the peak related to on-edge donors is still significant, a situation that is very well reflected in our results. On the other hand, a remarkable difference in the total absorption probability is the absence of the peak structure associated with impurities located at wells for quantum dots with radii less than 500 A with quantum wells and quantum well wires.

(ftro-eg) (meV)

Figure 53. Total optical absorption spectra (in units of W0), as a function of the hw — sg, for valence to donor transitions in infinite GaAs-(Ga,Al)As quantum dots of different radii. r0 = 3000 A (a) and r0 = 500 A (b) for a quantum dot with a homogeneous distribution of impurities, where there is no interaction between them. Reprinted with permission from [205], J. L. Marín et al., in "Handbook of Advanced Electronic and Photonic Materials and Devices" (H. S. Nalwa, Ed.). Academic Press, San Diego, 2001. © 2001, Academic Press.

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