Defect reactions and lattice relaxation in phosphorus-doped hydrogenated amorphous silicon studied by optical and thermal junction capacitance techniques
The first part of this study tested the accuracy of certain classes of proposed defect reactions in n-type hydrogenated amorphous silicon (a-Si:H). The Fermi level position, E[sub F], concentration of deep defects, N[sub D], and number of occupied conduction band tail states, N[sub BT], were varied by light soaking followed by thermal annealing treatment at successively higher temperatures. Samples were also quench cooled from 200[degrees]C. Drive-level capacitance profiling was used to measure N[sub BT] in phosphorus-doped a-Si:H. The corresponding N[sub D] was determined by thermally-stimulated capacitance in conjunction with voltage-pulse photocapacitance measurements. Previously proposed defect reactions predict a specific correlation between the change in N[sub D] and the accompanying change in N[sub BT]. The author's results show that these quantities can vary independently so that no single reaction adequately describes the measured changes. In the second part of this study, the author examined how the deep defect energy distribution and carrier emission dynamics were affected by altering E[sub F] in lightly-doped n-type samples. The author found an unexpected optical transition near 1.3 eV when E[sub F] = E[sub C] - 0.55 [+-] 0.08 eV. The author then explored the optimum measurement conditions for the observation of the 1.3 eV transition and examined its temporal evolution as a function of temperature. Complementary thermal capacitance emission transients showed that E[sub D] increased with voltage filling pulse width, up to a limiting energy near midgap, suggesting that E[sub D] increased with the average electron residence time on a defect. This behaviour signifies lattice relaxation in response to a change in the defect's charge state. This result can account for the conflicting transition energies measured by different research groups, discordant reports for the total system correlation energy, and the low luminescence efficiency of a-Si:H.
- Research Organization:
- Oregon Univ., Eugene, OR (United States)
- OSTI ID:
- 7044938
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SILICON
CAPACITANCE
DEFECTS
SPIN-LATTICE RELAXATION
AMORPHOUS STATE
DOPED MATERIALS
N-TYPE CONDUCTORS
PHOSPHORUS
SILANES
ELECTRICAL PROPERTIES
ELEMENTS
HYDRIDES
HYDROGEN COMPOUNDS
MATERIALS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
PHYSICAL PROPERTIES
RELAXATION
SEMICONDUCTOR MATERIALS
SEMIMETALS
SILICON COMPOUNDS
360606* - Other Materials- Physical Properties- (1992-)
665400 - Quantum Physics Aspects of Condensed Matter- (1992-)