Type of Document Dissertation Author Weerasekara, Aruna Bandara Author's Email Address aweerasekara1@student.gsu.edu URN etd-08022007-203605 Title ELECTRICAL AND OPTICAL CHARACTERIZATION OF GROUP III-V HETEROSTRUCTURES WITH EMPHASIS ON TERAHERTZ DEVICES Degree Ph.D. Department Physics and Astronomy Advisory Committee
Advisor Name Title A. G. U. Perera Committee Chair D. Edwards Committee Member D. Gies Committee Member G. Cymbalyuk Committee Member M. Stockman Committee Member N. Dietz Committee Member Keywords
- Quantum efficiency
- Dielectric function
- Dark current
- Responsivity
- Plasma frequency
- Neuron-like pulses
- High frequency dielectric constant
- Negative differential resistance
- Correlation dimension
- Embedding dimension
- Bifurcation.
- Return maps
- Arrhenius
- Dielectric function
- Absorption coefficient
- Absorption coefficient
- Detectors
- Terahertz
- Optical Phonon
- Infrared
Date of Defense 2007-07-18 Availability unrestricted Abstract Electrical and optical characterizations of heterostructures and thin films based on group III-V compound semiconductors are presented. Optical properties of GaMnN thin films grown by Metalorganic Chemical Vapor Deposition (MOCVD) on GaN/Sapphire templates were investigated using IR reflection spectroscopy. Experimental reflection spectra were fitted using a non - linear fitting algorithm, and the high frequency dielectric constant (ε∞), optical phonon frequencies of E1(TO) and E1(LO), and their oscillator strengths (S) and broadening constants (Γ) were obtained for GaMnN thin films with different Mn fraction. The high frequency dielectric constant (ε∞) of InN thin films grown by the high pressure chemical vapor deposition (HPCVD) method was also investigated by IR reflection spectroscopy and the average was found to vary between 7.0 - 8.6. The mobility of free carriers in InN thin films was calculated using the damping constant of the plasma oscillator.
The terahertz detection capability of n-type GaAs/AlGaAs Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) structures was demonstrated. A threshold frequency of 3.2 THz (93 µm) with a peak responsivity of 6.5 A/W at 7.1 THz was obtained using a 0.7 µm thick 1E18 cm−3 n - type doped GaAs emitter layer and a 1 µm thick undoped Al(0.04)Ga(0.96)As barrier layer. Using n - type doped GaAs emitter layers, the possibility of obtaining small workfunctions (∆) required for terahertz detectors has been successfully demonstrated. In addition, the possibility of using GaN (GaMnN) and InN materials for terahertz detection was investigated and a possible GaN base terahertz detector design is presented.
The non - linear behavior of the Inter Pulse Time Intervals (IPTI) of neuron - like electric pulses triggered externally in a GaAs/InGaAs Multi Quantum Well (MQW) structure at low temperature (~10 K) was investigated. It was found that a grouping behavior of IPTIs exists at slow triggering pulse rates. Furthermore, the calculated correlation dimension reveals that the dimensionality of the system is higher than the average dimension found in most of the natural systems. Finally, an investigation of terahertz radiation efect on biological system is reported.
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