On intersubband absorption of radiation in delta-doped QWs

The results of calculation of intersubband absorption coefficients for either center-, or edge-delta-doped with Phosphorus 10 nm and 20 nm-wide Si_0.8Ge_0.2/Si/Si_0.8Ge_0.2 quantum wells are presented. It is shown, that the absorption for delta-doped structures differs substantially from that of a pure rectangular or uniformly doped ones. There are two main features for delta-doped quantum wells. The first one is the blue-shift for optical transitions between first and others (more pronounced), and second and others (less pronounced) space quantized energy levels. The second one is that edge doping changes the symmetry of the quantum well and forbidden optical transitions for the rectangular structure become now allowed. The influences of temperature, quantum well width, and impurity concentration on the optical absorption are studied. It is shown that the most dramatic changes in comparison with rectangular quantum wells are for wider investigated edge-doped structures with bigger number of ionized impurities.