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Research was conducted to examine the effects of impurity states associated with heterostructures on the absorption of ultrasound. The objective of the study was to set up a calculation for the photostimulated ultrasound absorption by acceptor impurities in GaAs/Ga(sub 1-x)Al(sub x)As quantum wells. Results demonstrate that any device made from quantum well systems can be utilized as efficient traveling-wave detectors for ultrasound.

Research was conducted to examine the effects of atomic bond structure at the deposition surface on the crystallographic orientation dependence of carbon doping in gallium arsenide (GaAs). GaAs epilayers were prepared from semi-insulating GaAs substrates by atmospheric pressure in a vertical quartz reactor while epitaxial growths were carried out on different misoriented GaAs substrates. Results indicated CBr4 and CCl4 as excellent sources for the carbon doping of GaAs.

Reactivation rate of shallow SiGa donors in GaAs increases in an applied electric field. Post-hydrogenation anneals are involved in this procedure. The deep donor SiGa-H demonstrates dissociation in the ionized state and has a 0/+ level of Ec-0.75 electron volts. The Schottky diode, with a depletion region under zero and reverse bias, influences the dissociation rate.

The lattice location of Si impurity atoms in GaAs(100) crystals was investigated by means of the x-ray standing wave method. Experiments were performed wherein molecular beam epitaxy(MBE)-doped, ion-implanted and Si diffusion samples were subjected to a monochromatic x-ray beam. A curve fitting algorithm was then used to measure the photoionization rate of the Si impurities. Results show that the Si fluorescence signal is minimal in the MBE-doped samples.

The effect of doping and residual impurities on the electrical properties of GaAs epitaxial layers grown by closed-space vapor tranport (CSVT) technique is studied. The layers are grown from various negative- or positive-type doped GaAs sources using H2O as transport agent. The layers' charge densities and mobilities are then obtained by spectroscopic and Hall-effect measurements. Results indicate that various impurities, such as C, O, Si, Ge and S, have adverse effects on thee conductivity of GaAs layers.

Binary collision approximation was used to formulate a computer simulation of the Si implantation efficiency, Si depth profile and the vacancy formation for Si-implanted GaAs(001) crystals. The results of the Si depth profile calculations coincided with experimental results derived from secondary-ion mass spectroscopy. However, the simulated distribution of vacancies in the simulation were shallower and the Ga vacancies exceeded the number of As vacancies. These results indicate that Si atoms easily occupy Ga sites and are activated as donors.

Samples irradiated with one MeV and thermal neutrons and with seven MeV and white electrons at various fluences were used to obtain the broadening parameter of the reflectance peak of the free exciton in GaAs at 17 kelvin. The lifetime of the free exciton as a function of the fluence has been explained by a simple kinetics model which applies also to epitaxial layers. The radius associated with the cross section calculated from the damage coefficients is of the order of three to ten times that of the excitons.

Results of a Monte Carlo simulation of electron transitions causing the temperature dependence of slightly doped semiconductor spectral linewidths is discussed. Photothermal magnetospectroscopic studies of impure semiconductors showed linewidth broadening as electron redistribution occured with increasing semiconductor temperature. A simulation of the semiconductors' impurity band was done to obtain the electrons temperature-dependent distribution function. The algorithm used for the simulation is given and the results of the simulations were used to validate theoretical studies. Accuracy of theoretical studies can only be achieved by the method at present.

The effect of hydrogenation on Si- and Be- ion implanted GaAs exposed to the hydrogen plasma was analyzed. The results show that for a sample hydrogenated for 60 minutes, electron movement increased by 21% at 300K and 1400 cu.cm/V s at 150 K. The electron and hole traps at Ec-0.62- and Ev+0.68-eV levels were decreased during room temperature hydrogenation. This effect was also seen whenthe material was annealed at 400 degrees centigrade for five minutes in an argon ambient.

Small quantities of microscopic ferromagnetic grains of gallium-manganese are deposited in the gallium arsenide semiconducting matrix using high energy manganese ions and thermal treatment. Unusually high magnetoresistance is observed in the doped semiconductors. Advantages of unique magnetic properties of the ferromagnetic-doped semiconductors such as spin superlattices are discussed.