Matching Items (2)
Description
In this work, an advanced simulation study of reliability in millimeter-wave (mm-wave) GaN Devices for power amplifier (PA) applications is performed by means of a particle-based full band Cellular Monte Carlo device simulator (CMC). The goal of the study is to obtain a systematic characterization of the performance of GaN devices operating in DC, small signal AC and large-signal radio-frequency (RF) conditions emphasizing on the microscopic properties that correlate to degradation of device performance such as generation of hot carriers, presence of material defects and self-heating effects. First, a review of concepts concerning GaN technology, devices, reliability mechanisms and PA design is presented in chapter 2. Then, in chapter 3 a study of non-idealities of AlGaN/GaN heterojunction diodes is performed, demonstrating that mole fraction variations and the presence of unintentional Schottky contacts are the main limiting factor for high current drive of the devices under study. Chapter 4 consists in a study of hot electron generation in GaN HEMTs, in terms of the accurate simulation of the electron energy distribution function (EDF) obtained under DC and RF operation, taking into account frequency and temperature variations. The calculated EDFs suggest that Class AB PAs operating at low frequency (10 GHz) are more robust to hot carrier effects than when operating under DC or high frequency RF (up to 40 GHz). Also, operation under Class A yields higher EDFs than Class AB indicating lower reliability. This study is followed in chapter 5 by the proposal of a novel π-Shaped gate contact for GaN HEMTs which effectively reduces the hot electron generation while preserving device performance. Finally, in chapter 6 the electro-thermal characterization of GaN-on-Si HEMTs is performed by means of an expanded CMC framework, where charge and heat transport are self-consistently coupled. After the electro-thermal model is validated to experimental data, the assessment of self-heating under lateral scaling is considered.
ContributorsLatorre Rey, Alvaro Daniel (Author) / Saraniti, Marco (Thesis advisor) / Kitchen, Jennifer (Committee member) / Goodnick, Stephen M (Committee member) / Thornton, Trevor (Committee member) / Arizona State University (Publisher)
Created2018
Description
The continuous demand for higher power density and better efficiency to reduce the global energy consumption, is the driving force to introduce new semiconductor technologies. Wide-band-gap (WBG) material based devices such as gallium nitride high electron mobility transistors (GaN HEMTs) and silicon carbide metal-oxide-semiconductor field-effect transistors (SiC MOSFETs) are considered promising candidates for replacing conventional silicon MOSFETs, mainly because of their capabilities of higher switching frequencies with less switching and conduction losses. Although WBG devices can largely improve the conversion efficiency, the implementation of WBG devices brings in some challenges in power converter design. Firstly, the high voltage changing slew rate of WBG devices introduces a distortion current to the gate through the coupling capacitance of the device. The distortion current may cause mis-trigger or overvoltage breakdown of the device gate. This issue is so-called crosstalk effect. This dissertation proposes a multilevel gate driving profile to address this issue.
Secondly, due to the gate-to-substrate voltage bias, the integration of multiple GaN devices suffers from the high on-state resistance. This issue is so-called current collapse or electron trap. This dissertation proposes a gate current injection method to address this issue. By injecting relatively large gate current at specific time period, the on-state resistance is largely improved at both hard-switching and soft-switching scenarios.
Thirdly, series connection of switches is an effective way to achieve higher blocking voltage of the device. The serial connection of WBG devices suffers from the dynamic voltage unbalance and short-circuit protection issues. The additional short-circuit scenarios are found in the series-connected devices, which are not covered by the traditional short-circuit protection scheme. Dynamic voltage sharing problem is addressed using porposed current source gate driver. Besides, the short-circuit protection circuit is integrated in the proposed gate driver to cover all the short-circuit scenarios of series-connected devices.
Finally, this dissertation uses a practical converter design example to comprehensively elaborate the design considerations of WBG based converters. A 1.5 MHz/ 2 kV/ 80 A commercial burst-mode inverter using SiC MOSFETs is designed for electromagnetic acoustic transducer. This inverter design includes comprehensive fault protection, hardware and controller design.
ContributorsLiu, Chunhui (Author) / Lei, Qin QL (Thesis advisor) / Ayyanar, Raja RA (Committee member) / Ranjram, Mike MR (Committee member) / Mallik, Ayan AM (Committee member) / Arizona State University (Publisher)
Created2022