The high energy states of a shallow donor in a GaAs/ Ga0.7Al0.3As multiple quantum well structure under perpendicular magnetic fields are studied both theoretically and experimentally. The effects due to Coulomb coupling between different confinement subbands and the electron-phonon interaction are investigated. We show that most of the absorption peaks in the IR-PC spectrum are due to direct transitions from the ground state to the m = 1 states associated with the first subband. The remaining absorption peaks are explained by phonon-assisted harmonics.

The high pressure diamond anvil cell can be used for Fourier Transform Magneto-Spectroscopy of impurity levels in semiconductors at far infrared wavelengths. The performance of the diamond anvil cell for this type of spectroscopy is evaluated. In the present measurements we investigate the non-metastable impurity states in n-type AlxGa1-xAs materials in the frequency range 80-300 cm-1 up to a maximum pressure of 45 kbar. A shallow to deep transition of an impurity in undoped n-type Al0.03Ga0.97As was observed at approximately 22kbar. This non-metastable state is either non-lattice relaxed or is weakly relaxed and is resonant with the conduction band at atmospheric pressure. In lightly silicon doped n-type GaAs the crossover from the shallow donor state to the non-metastable silicon A1 antibonding level occurred at 25 kbar.

Fe epitaxial films were grown on Si(100) substrate by MOCVD using thermal decomposition of iron pentacarbonyl, Fe(CO) 5 . X-ray diffraction and XPS spectroscopy were used to study the structure of the epitaxial film. The results indicate that single crystal Fe film and iron oxide-iron-silicon multilayer structure can be grown on Si (100) substrate. We have also discussed the relation between microstructure and MOCVD process.

Frequency domain studies of intersubband transitions have been carried out with a FIR Fourier Transform Spectrometer. The experimental techniques have been applied to several studies including subband spectroscopy in (100) and vicinal planes, and in (111) and (110) inersion layers as well as the effects of oxide charge on the optical properties of (100) inversion layers.

Cyclotron-resonance experiments on inversion-layer electrons in a series of large gate area Si metal-oxide-semiconductor field-effect transistors (MOSFET's) have been performed with a submillimeter laser system in conjunction with high-field Bitter-type magnets. The parameters determined from fits to the experimental magnetotransmission data, cyclotron effective mass and scattering time, have been studied as functions of laser wavelength, resonant magnetic field, inversion-layer density, temperature, and depletion charge. Results exhibit consistent and systematic behavior from sample to sample as functions of these various parameters. There are two distinct regions of density with different physical behavior. In both the high-density (metallic) and low-density (localized) regimes the experimental results appear to be influenced largely by electron-electron interactions. A transition region between these two extremes also exhibits distinctive behavior. These results are compared with other work, and possible explanations are discussed.

Fourier Transform Spectroscopic studies of inter-electric-field subband transitions in Silicon inversion layers are compared with optical properties calculated with a 5 media model and a classical dielectric function representation of the inversion layer. Qualitative discrepancies in relative intensities of the subband transitions are interpreted in terms of many-body effects.

A discussion is given of the effect of light and temperature on experiments performed to determine the cyclotron effective mass. Mass shifts at moderate and high densities in the presence of light are accounted for by a shift in inversion layer density. The mass decreases with increasing temperature at moderate densities and increases with temperature at low densities approaching 0.19 m0 in both cases.

Surface channel tunnel junctions (SCTJ) can be fabricated by replacing the usual degenerate n-type source contact on a weakly p-type substrate by a highly degenerate p-type source. In the presence of a gate voltage strong enough to produce a surface inversion layer, a tunnel junction connecting the three-dimensional p+ source and the quasi-two-dimensional n-type surface channel can occur. The I-V characteristics of this SCTJ will yield valuable information about the subband splittings and other electronic properties of the surface inversion layer.

Photoluminescence, photoluminescence excitation, and optical absorption measurements have been carried out on semi-insulating and n-type InP:Fe. Interband excitation of the ~0.35 eV intracentre Fe2+ transition is interpreted in terms of electron capture by an Fe3+, resulting in an Fe24+ centre in the 5T2 excited state, which relaxes radiatively to the 5E ground state. An extrinsic band in the photo luminescence excitation spectrum of the ~ 0.35 eV luminescence exhibits an onset at ~ 1.13–1.15 eV, which is attributed to transitions from the valence band to the 5T2 excited state of Fe2+. This assignment is found to be consistent with the energy level scheme for InP:Fe proposed by Fung, Nicholas and Stradling.

The density and temperature dependences of high frequency/resonant field (61.3 cm-1, 11T) resonant magnetoabsorption data in (100) Si inversion layers at low densities are strikingly different from those observed at lower frequencies/fields. The results, which include a dramatic resonant line narrowing at high fields, are discussed in light of single-electron localization and the possibility of a cooperative electronic transition assisted by the large magnetic field.

Photoluminescence techniques have been used to detect and characterize p-type conducting layers formed on the surface of semi-insulating GaAs substrates and at the liquid phase epitaxial layer–GaAs substrate interface during pregrowth heat treatment. These layers contain ∼1017 cm−3 shallow acceptors and a high density of arsenic vacancy complexes, and can be eliminated by pregrowth Ga etching of the substrate.

Photoluminescence spectra from ion-implanted Be acceptors in GaAs have been studied as a function of wavelength and intensity of excitation light over the implant-fluence range 3×1012 to 1×1015 cm−2. It is demonstrated that the nonuniform distributions of implantant concentration as a function of depth in the implanted layer produce a profiling effect which causes anomalous changes in photoluminescence line shapes and energy positions as a function of excitation intensity. These results imply photoexcited carrier diffusion lengths of much less than 1 μm in implanted and annealed layers in bulk GaAs.