Engineering Commons^™

Investigating Operational Modes In Gallium Nitride Photoconductive Switches, Brad J. Maynard

Electrical and Computer Engineering ETDs

As switching requirements for speed, power, and efficiency become more stringent, advances in wide-bandgap (WBG) materials has enabled their use in high power switching devices. One such device, the photoconductive semiconductor switch (PCSS), while previously constructed from GaAs, shows promise using WBG Mn-doped GaN. Lateral and vertical geometries of PCSS have been produced and evaluated for operation using sub-mJ/ns regime pulsed laser incidence. At fields below 25 kV/cm, the lateral switch operates in the linear regime where modest photocurrent fitting the laser envelope is observed. Above this threshold, the switches demonstrate circuit-limited persistent conductivity (PC) current, in what is presumed …

Etched-And-Regrown Diodes On M-Plane Gan For Next Generation Power Electronic Devices, Andrew A. Aragon

Electrical and Computer Engineering ETDs

Demand for next-generation power electronic devices is driven by continually evolving requirements of power systems. Devices utilizing III-nitride materials (GaN) and vertical selective-area doped architectures are advantageous due to their wide- bandgap, thermal management, small form-factor, and current handling.

Such devices incorporate junctions at multiple crystalline planes. Thus, effects of impurity contamination and etch damage are investigated on the m-plane (10-10) of GaN. Impurites (Si, O, and C) are shown to reduce blocking voltage (~ 10² ×) and increase forward leakage current (~ 10⁴ ×) in regrown versus continuously-grown p-n diodes. Elevated deep level defects at Ec – …

Nonpolar Gan-Based Vcsels With Lattice-Matched Nanoporous Distributed Bragg Reflector Mirrors, Saadat M. Mishkat-Ul-Masabih

Electrical and Computer Engineering ETDs

Wide-bandgap optoelectronic devices have undergone significant advancements with the advent of commercial light-emitting diodes and edge-emitting lasers in the violet-blue spectral region. They are now ubiquitous in several lighting, communication, data storage, display, and sensing applications. Among the III-nitride emitters, vertical-cavity surface-emitting lasers (VCSELs) have attracted significant attention in recent years due to their inherent advantages over edge-emitting lasers. The small active volume enables single-mode operation with low threshold currents and high modulation bandwidths. Their surface-normal device geometry is conducive to the cost-effective formation of high-density 2D arrays while simplifying on-chip wafer testing. Furthermore, the low beam divergence and circular …

Characterization Of Gallium Nitride Photoconductive Semiconductor Switches In The Nonlinear Regime, Joseph D. Teague

Electrical and Computer Engineering ETDs

The energy demands of an increasingly electrified world have caused a renewed interest in once dormant fields of research. Photoconductive Semiconductor switches (PCSS) are one of these fields. They theoretically offer high voltage, high current switching in sub cm³ packaging, without the shot to shot variation and bulk of current high-power DC switches such as spark gaps. PCSS are capable of power densities of 10⁹-10¹⁰ W/cm³, with electric fields ranging from 10⁵-10⁶ V/cm and current densities from 10⁴-10⁶ A/cm² [1].

Most PCSS make a trade-off between voltage, …