Optical phonon sidebands of electronic intersubband absorption in strongly polar semiconductor heterostructures.

We present the first evidence for a distinct optical phonon progression in the linear and nonlinear intersubband absorption spectra of electrons in a GaN/Al(0.8)Ga(0.2)N heterostructure. Femtosecond two-color pump-probe experiments in the midinfrared reveal spectral holes on different vibronic transitions separated by the LO-phonon frequency. These features wash out with a decay time of 80 fs due to spectral diffusion. The remaining nonlinear transmission changes decay with a time constant of 380 fs. All results observed are described by the independent boson model.

Sample preparation technique for cross-sectional transmission electron microscopy of quantum wire structures.

A novel cross-sectional sample preparation technique for quantum wire (QWR) structures is described. By coating a thin layer of Au with a designed pattern on the sample as a marker to indicate the position of the wire pattern, the location of the thinned area can be controlled precisely. An example of applying this technique to an InGaAs/GaAs QWR structure is demonstrated. This technique can also be applied to any other small dimensional structures or devices with specific regions of interest.