Complete electrical study of recombination properties of titanium and zinc deep levels in silicon
Wang, Alex Chikuo
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https://hdl.handle.net/2142/25297
Description
Title
Complete electrical study of recombination properties of titanium and zinc deep levels in silicon
Author(s)
Wang, Alex Chikuo
Issue Date
1984
Doctoral Committee Chair(s)
Sah, C.T.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
electrical study
recombination
titanium
zinc
silicon
hole recombination
deep level traps
semiconductors
Language
en
Abstract
"Energy exchange mechanisms of electron and hole recombination at deep level traps in semiconductors are studied. New variations of the capacitance and current transient techniques are developed which overcome two major experimental limitations: (1) capture is too fast, and (2) optical excitation and specially designed samples seem necessary. They permit purely electrical measurements of all relevant band-bound quantum-mechanical transition rates. The data strongly indicate that the dominant energy exchange is through a nonradiative multiphonon mechanism, but the temperature dependence and magnitude of the carrier capture rate below room temperature are largely determined by the charge state of the trap.
Titanium and zinc in silicon were chosen for this study following a ""try the simplest case"" philosophy. Titanium in silicon is the simplest deep trap system that is ideal for testing the charge state effect but also challenges experimentalists by possessing both major limitations stated above. It is demonstrated that with the new electrical measurements, all majority and minority carrier capture rates in zero field as well as the emission rates of the Ti double-donor levels can be directly obtained on a single n+/p diode. The capture rate data confirm the charge effect.
Zinc in silicon is the simplest system that is ideal for elucidating
two major outstanding questions in recombination physics and thereby ascertaining the multiphonon mechanism. (1) For two decades it has been suspected that the carrier capture rates associated with many multicharge-state centers were due to a local Auger mechanism. It is shown that this postulate can be experimentally tested, and for Zn in Si the Auger effect plays negligible role'. (2) The comparison of capture rate data with the multiphonon theory has been in doubt for repulsive centers since the effect of the electronic barrier was not quantitatively known. It is shown that this effect is dictated by the Sommerfeld factor for
tunneling through the screened Coulomb barrier, and failure by other workers to recognize this caused an overemphasis of lattice relaxation."
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