2026-09-23T02:59:58Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/25788 2023-07-10 col_2142_8859 col_2142_5131 com_2142_8858 com_2142_234 com_2142_5130

Sah, C.T. Tasch, Aloysious Felix 2011-07-13T14:46:30Z 2011-07-13T14:46:30Z 10000-01-01 1969 A new method for studying the recombination-generation and optical behavior of impurities in semiconductors is presented. This method is known as the impurity photovoltaic effect. The basic idea of the impurity photovoltaic effect is to study the photo-response of a reverse biased PIN junction that, is doped with the impurity of interest. The energy of the incident photons is less than, the forbidden energy band·gap but greater tban the impurity ionization energy. From the photocurrent it is possible to determine the thermal emission (or generation) rates and photoionization cross sections of carriers from the impurity centers! This information may be obtained without knowledge of the impurity concentration. The impurity photovoltaic effect is applied to study the acceptor level of gold in silicon. The thermal ,emission rates of electrons and holes from negatively ionized and neutral gold atoms, respectively, are determined as a function of temperature in the range 1950 -300oK. It is concluded that the gold is mostly in the neutral charge state in the depletion region of a PN junction. Capture rates and capture cross sections are also deduced ,from the thermal emission rates. The results are not too definite since they are sensitive to the exact location of the gold acceptor level and the degeneracy factor associated with the acceptor level. The electric field dependence of the thermal emission rates is measured and can be explained qualitatively by the Poole-Frenkel effect. The measured field dependences are compared with the field dependence· calculated from the Poole-Frenkel model for Coulomb, square well, and polarization potentials. Partial agreement with the square well and polarization potentials is obtained, indicating that the impurity potential as seen by an electron or hole is not of the long range Coulomb type. Rather it appears to be short range in nature. The photoionization cross sections of electrons and holes from negatively charged and neutral gold atoms are also measured in the spectral range .57-.8gev. The hole photoionization cross section is compared with an expression derived by Lucovsky. Thea greement is fairly good for reasonable choices of the effective field ratio and the effective mass of the bcmnd hole. The electron photoionization cross section is compared with a theoretical expression derived by Eagles and Dumke. The agreement is poor and is probably.due to the deviation of gold in silicon from the model and assumptions employed by Eagles and Dumke. The photoionization cross sections are checked for electric field dependence. There appears to be little or no field dependence in the range 3-14xlO 4 volts/cm. The location of the acceptor level is estimated from the spectral dependence of the photoionization cross sections. The result of .53-.55ev for the location of the acceptor level below the conduction band is in good agreement with the other reported results, The theory for the impurity photovoltaic effect is analyzed with the donor level included. The results are compared with those that follow from the single-level treatment. The comparison indicates that the single7level treatment is a very good approximation for photon energies less than .8ev, Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-07-13T14:46:30Z No. of bitstreams: 1 1969_tasch.pdf: 8401374 bytes, checksum: 6bf9e6557080c2f7e9eebff71ee2d4e5 (MD5) Made available in DSpace on 2011-07-13T14:46:30Z (GMT). No. of bitstreams: 1 1969_tasch.pdf: 8401374 bytes, checksum: 6bf9e6557080c2f7e9eebff71ee2d4e5 (MD5) Previous issue date: 1969 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-07-13T14:46:30Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:32:46-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 6067277 http://hdl.handle.net/2142/25788 en 1969 Aloysious Felix Tasch, Jr. thermal emission rates optical cross sections carriers at gold centers silicon impurity photovoltaic effect recombination generation optical behavior of impurities Studies of thermal emission rates and optical cross sections of carriers at gold centers in silicons using the impurity photovoltaic effect Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.