The bandgap and band-edge effective mass of single crystal cadmium oxide, epitaxially grown by metal-organic vapor-phase epitaxy, are determined from infrared reflectivity, ultraviolet/visible absorption, and Hall effect measurements. Analysis and simulation of the optical data, including effects of band nonparabolicity, Moss-Burstein band filling and bandgap renormalization, reveal room temperature bandgap and band-edge effective mass values of 2.16± 0.02 eV and 0.21± 0.01m 0 respectively.

The valence-band density of states of single-crystalline rock-salt CdO͑001͒, wurtzite c-plane ZnO, and rocksalt MgO͑001͒ are investigated by high-resolution x-ray photoemission spectroscopy. A classic two-peak structure is observed in the VB-DOS due to the anion 2p-dominated valence bands. Good agreement is found between the experimental results and quasi-particle-corrected density-functional theory calculations. Occupied shallow semicore d levels are observed in CdO and ZnO. While these exhibit similar spectral features to the calculations, they occur at slightly higher binding energies, determined as 8.8 eV and 7.3 eV below the valence band maximum in CdO and ZnO, respectively. The implications of these on the electronic structure are discussed.

Electron accumulation states in InN have been measured using high resolution angle-resolved photoemission spectroscopy (ARPES). The electrons in the accumulation layer have been discovered to reside in quantum well states. ARPES was also used to measure the Fermi surface of these quantum well states, as well as their constant binding energy contours below the Fermi level E(F). The energy of the Fermi level and the size of the Fermi surface for these quantum well states could be controlled by varying the method of surface preparation. This is the first unambiguous observation that electrons in the InN accumulation layer are quantized and the first time the Fermi surface associated with such states has been measured.

In contrast to conventional semiconductors, native defects, hydrogen impurities, and surface states are all found to be donors in n-type CdO. Using this as a model system, the electrical behaviors of defects, dopants, and surface states in semiconductors are unified by a single energy level, the charge neutrality level, giving much insight into current materials and allowing a band-structure engineering scheme for obtaining desired custom electronic properties in new compound semiconductors.

Bulk and surface electronic properties of Si-doped InN are investigated using high-resolution x-ray photoemission spectroscopy, optical absorption spectroscopy, and quasiparticle corrected density functional theory calculations. The branch point energy in InN is experimentally determined to lie 1.83± 0.10 eV above the valence-band maximum. This high position relative to the band edges is used to explain the extreme fundamental electronic properties of the material. Far from being anomalous, these properties are reconciled within chemical trends of common-cation and common-anion semiconductors.

The composition dependence of the Fermi-level pinning at the oxidized ͑0001͒ surfaces of n-type In x Ga 1−x N films ͑0 ഛ x ഛ 1͒ is investigated using x-ray photoemission spectroscopy. The surface Fermi-level position varies from high above the conduction band minimum ͑CBM͒ at InN surfaces to significantly below the CBM at GaN surfaces, with the transition from electron accumulation to depletion occurring at approximately x = 0.3. The results are consistent with the composition dependence of the band edges with respect to the charge neutrality level.

The valence-band structure of clean, high-quality, single-crystalline wurtzite InN thin films prepared with atomic hydrogen is investigated using x-ray photoemission spectroscopy. The In4d 5/2 semicore level due to the In-N bond is found to lie 16.0± 0.1 eV above the valence band maximum. Experimental valence-band spectra are compared with theoretical calculations of the valence-band density of states ͑VB-DOS͒, employing density functional theory within the local density approximation with quasiparticle and self-interaction corrections. Agreement between the experimental valence band spectrum and the theoretical VB-DOS is obtained.

Fourier transform infrared absorption measurements are presented from the dilute nitride semiconductor GaNSb with nitrogen incorporations between 0.2% and 1.0%. The divergence of transitions from the valence band to E − and E + can be seen with increasing nitrogen incorporation, consistent with theoretical predictions. The GaNSb band structure has been modeled using a five-band k · p Hamiltonian and a band anticrossing fitting has been obtained using a nitrogen level of 0.78 eV above the valence band maximum and a coupling parameter of 2.6 eV. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2349832͔It is well documented that the anion substitution of dilute quantities of nitrogen into III-V semiconductor compounds results in a sharp decrease in the band gap of the material from that of the host compound. A number of explanations have been suggested to describe this band gap reduction, most notably the band anticrossing model ͑BAC͒, calculations based on empirical pseudopotential methods, and interpretations based on the mixing of the ⌫, L, and X character of the conduction band states. The origin of this band gap reduction is the isoelectronic nature of the nitrogen atoms in the host III-V material. Though the nitrogen atom has the same electron valence as the atom it is replacing, its physical properties ͑size, electronegativity, bond length, etc.͒ are significantly different, resulting in a considerable, highly localized perturbation to the electronic potential surrounding the atom.According to the BAC model this localized deformation in potential results in the formation of an energy level extended in k space which may be resonant with the conduction band of the host. The interaction between the host conduction band and resonant nitrogen level results in the formation of two nonparabolic subbands ͑conventionally denoted E − and E + ͒ given by the relationwhere V MN is the matrix element describing the coupling between the host conduction band ͑E M ͒ and the resonant nitrogen level ͑E N ͒ and has the functional form V MN = C MN ͱ x where C MN is the coupling parameter and x is the nitrogen concentration. 2Nitrogen induced band gap reduction has been observed in many alloys including GaNP, 3 GaNAs, 4 InNAs, 5 and most recently GaNSb. 6 The addition of antimony to the dilute nitride GaNAs has been shown to improve the optical and electronic properties of the material 7 and has been suggested as a possible material for long wavelength optoelectronic devices lattice matched to GaAs. 8 To determine the dependence of the band gap of such materials as a function of nitrogen incorporation, the BAC parameters of the constituent endpoint ternaries must be known. Though these have been well investigated in GaNAs a lack of data is found for GaNSb, a fact highlighted in Vurgaftman and Meyer's review on nitrogen containing III-V materials. 9In this letter, Fourier transform infrared ͑FTIR͒ absorption measurements of GaNSb samples with nitrogen incorporations between 0.2% and 1.0% are presented and preliminary values f...