Dietrich W. Langer

Energy Terms of ZnS:Tm and Ho

The absorption and emission spectra of ZnS:Tm3+ and Ho3+ were observed at 4.2°, 77°, and 290°K between 3400 and 9000 A by using a high‐dispersion spectrograph. The L—S coupling terms of Tm3+ and Ho3+ were determined and the spin—orbit interaction term ζ and the Slater integral F2 were estimated for Tm to be 2702 and 440 cm—1, respectively. Also the crystal field splitting terms and the pressure dependence of absorption and emission are discussed in this paper.

Temperature and Pressure Dependence of the Index of Refraction of CdS

By transmission measurements on CdS platelets the locations of interference maxima were determined between the absorption edge and 6500 A for E⊥C and E∥C. As temperature and pressure around the sample were changed the displacement of these maxima was followed. Subsequently the dispersion curves were established. The temperatures were varied between 4.2° and 358°K at atmospheric pressure and between 77° and 358°K at hydrostatic pressures up to 10 kbar. The quantities dn⊥/dλ and dn∥/dλ which might be useful for laser applications are presented.

Stimulated Emission and Excited States of the I6 Donor Electron in ZnO

Laser‐excited luminescence has been measured in ZnO at 1.2°K. Emission due to the annihilation of the I6 bound excition with simultaneous excitation or ionization of the donor electron has been observed in stimulated emission, which was excited by intense N2 laser light. From the hydrogenlike series of these emission lines, the binding energy and the effective mass of the donor electron are estimated to be 40 meV and 0.22m, respectively.

Stimulated Emission Spectra of CdS Platelets under Various Excitation Levels

The stimulated emission of CdS platelets excited by light pulses from a N2 laser is investigated at 2° and 77°K, as a function of the level of excitation and for differently prepared crystals. Pure and perfect crystals show peaks due to exciton‐exciton interactions (P), and due to the recombination of a free exciton with simultaneous emission of one or two LO phonons [(Ex‐LO) and (Ex‐2L)]. Platelets grown in an atmosphere of excess S or Cd show up to five additional stimulated emission lines, located between P and Ex‐LO. Imperfect crystals show a broad emission band extending from P to beyond Ex‐LO. At low excitation levels only P appears in the stimulated emission spectra. With increasing level of excitation the intermediate impurity lines (JJ) in Cd‐ and S‐rich crystals also show stimulated emission and the maximum emission intensity shifts from the P peak sequentially through all JJ lines always toward the next peak at lower wavelengths. At still higher excitation levels, Ex‐LO, the next peak at lower ...

Excimer and dye laser annealing of silicon‐nitride‐capped, Si‐implanted GaAs

Carrier concentrations exceeding 1019/cm3 in GaAs implanted with Si (2×1014/cm2 at 140 keV) have been obtained by pulsed laser annealing with either a dye laser (λ=728 nm) or a XeCl excimer laser (λ=308 nm). Dye‐laser annealing through a ∼55‐nm‐thick Si3N4 cap consistently produced higher activations than excimer‐laser annealing with or without the cap. Carrier densities were measured by phonon‐Raman and plasmon‐Raman scattering.

Linear Compressibilities of II‐VI Compound Single Crystals

The isothermal linear compressibilities of the II‐VI compound single crystals, CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, and ZnTe were measured by an optical interferometer. The change in length of the crystals was obtained relative to iron under hydrostatic pressures between 1 and 10 kbar. A method was devised to measure small gaps to a fraction of a micron at room pressure to obtain the initial parameters of the interferometer.

Erratum: Index of Refraction of Isopentane and Mesitylene as a Function of Pressure

The change of the refractive index of isopentane was determined by an interferometric method at room temperature between 1 and 10 kbar, and of mesitylene—between 1 and 3.4 kbar, which is roughly its freezing point at room temperature. The results are combined with P − V data of Bridgman and compared to an equation by Bottcher, rendering average molecular radii and polarizabilities for these two substances.

Defect studies in multilayer epitaxial GaAs by transient capacitance

Majority‐carrier defects, induced by 1‐MeV‐electron irradiation in n‐type epitaxial GaAs were studied by deep‐level‐trap spectroscopy. The samples were fabricated in the form of FET‐like devices on the epitaxial active and buffer layers. Anomalies in the DLTS response such as the appearance of double peaks, a rapid growth of transient response, and lack of exponential behavior as the depletion width extends into the buffer are discussed in terms of the planar geometry, the series resistance, and the multilayer nature of the devices.