Terahertz Generation in Submicron Nitride-based Semiconductor Devices

GaN;nitride;THz

Barry, Edwin Allen ; Ki Wook Kim, Committee Chair,Ralph C. Smith, Committee Member,Douglas W. Barlage, Committee Member,Robert J. Trew, Committee Member,Barry, Edwin Allen ; Ki Wook Kim ; Committee Chair ; Ralph C. Smith ; Committee Member ; Douglas W. Barlage ; Committee Member ; Robert J. Trew ; Committee Member

University:North Carolina State University

关键词: GaN;    nitride;    THz;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/3566/etd.pdf?sequence=1&isAllowed=y

美国|英语

来源: null

【 摘 要 】

In this thesis, the electron dynamics and transport properties of III-nitride semiconductors materials and devices are studied, with an emphasis on their application to the generation high-frequency electromagnetic radiation. Numerical simulation models, including Monte Carlo, drift-diffusion, and thermal diffusion are utilized to model transport in the hot-electron and moderate-field regimes.The Monte Carlo method is first applied to the study of the distribution function and the basic characteristics of hot electrons in III-nitrides under moderate electric fields. It is found that in relatively low fields (of the order of kV/cm) polar-optical phonon emission dominates the electron kinetics giving rise to a spindle-shaped distribution function and an extended portion of a quasisaturation of the current-voltage (I-V) characteristics. The Monte Carlo program developed for the study of the III-nitrides is then extended to include the quantum mechanical spin evolution of electrons in bulk GaAs at room temperature. The spin relaxation time and characteristic decay lengths of spin polarized electrons are determined.Next, the conditions for microwave power generation in a submicrometer GaNdiode are investigated. By applying a high-field electron transport model based on the local quasistatic approximation, it is shown that oscillations in GaN diodes can be supported in the terahertz-frequency range near the LSAregime. The shape of the diode voltage and electronic currentwaveforms are examined in terms of the circuit parameters andoperating frequencies over the bandwidth of active generation. Basedon a Fourier series analysis of the diode voltage and current, thegenerated power and dc-to-RF conversion efficiency at thefundamental and the lowest higher harmonic frequencies areestimated. The calculation results clearly indicate thatsubmicrometer GaN diodes (channel doping of $1 imes 10^{17}$cm$^{-3}$) can achieve large output powers ($>$ 1 W) in the absenceof Gunn domain formation, over a wide range of frequencies, near 0.5terahertz.Finally, conditions for pulsed dc regimes of terahertz power generationare theoretically investigated in a vertical nanoscale $n^+nn^+$ GaN-based diodecoupled to an external resonant circuit. A combined electrothermal model is adopted allowing for a detailed analysis of the dynamical local distributions of the electric field, drift velocity, and lattice temperature viaself-consistent simulation of the high-field electron transport inthe active channel and the thermal transport in the devicestructure.The main performance parameters including, generationpower, efficiency, and operation frequency are determined forstable generation with short pulses of a few ns and afew tens of ns of duty cycle. The presented results can be used for optimization and design of two-terminal GaN-based high-power THzgenerators for pulsed regime operation.