Shallow acceptors in Ge/GeSi strained multilayer heterostructures with quantum wells

The impurity photoconductivity spectra of Ge/Ge_1−x Si_x strained heterostructures with quantum wells are investigated. It is established that the built-in deformation in quantum-size Ge layers substantially changes the spectrum of shallow acceptors, shifting it into the long-wavelength region of the far-IR range. In strong magnetic fields the photoconductivity lines are observed to split and shift as a function of the field. This makes it possible to carry out a classification of the transitions. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 2, 194–198 (25 January 1997)     

Searching for and Quantifying Nonconvexity Regions of Functions*

Lithuanian Mathematical Journal - Convexity plays a prominent role in a number of areas, but practical considerations often lead to nonconvex functions. We suggest a method for determining regions...     

Photoluminescence kinetics of structures with InAs quantum dots for IR photodetectors

The experimental results of a photoluminescence kinetics study of InAs/GaAs structures with quantum dots grown by metal-organic vapor-phase epitaxy are shown. The measurements have revealed the fast capture of excited carriers from the GaAs barrier to quantum dots and slow interlevel relaxation inside the quantum dots.     

Shallow acceptors in Ge/GeSi multi-quantum well heterostructures

The experimental spectra of residual shallow acceptors in strained quantum well Ge/GeSi heterostructures are interpreted on the basis of a new theoretical approach taking into account both confinement and strain effects. It is shown that the main lines in the spectra of undoped samples with narrow quantum wells result from the photoexcitation of the on-edge acceptors that have binding energy two times less than on-center acceptors.     

Estimation of Spectral Densities with Multiplicative Parameter

A two-step estimation procedure is presented for spectral densities of the form f()=g() with and being unknown parameters. The classes of random fields for which the procedure is applicable are defined by restrictions on spectral densities of second and higher orders. The procedure suggests a minimum contrast estimator for the parameter which is then used to construct the estimator for . The delta method provides the asymptotic normality of our estimator for the parameter .