Effects of Low-Mobility Holes in TCAD Simulated GaN/AlGaN/GaN Super-Heterojunction HEMT for RF and High-Power Applications
Open Access
- Author:
- Kemmerling, Jesse
- Graduate Program:
- Electrical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 18, 2021
- Committee Members:
- Rongming Chu, Thesis Advisor/Co-Advisor
Tom Jackson, Committee Member
Kultegin Aydin, Program Head/Chair - Keywords:
- gallium nitride
HEMT
super-heterojunction
field plate
RF amplifier
hole mobility
TCAD
microwave amplifier - Abstract:
- Wide-bandgap materials, such as gallium nitride (GaN), are becoming the forefront in high power and high frequency, microelectronics because of their large breakdown fields and high carrier mobilities. GaN and AlGaN are a popular combination of materials because their heterojunction creates a polarization induced high density and high mobility two-dimensional electron gas (2DEG). The characteristics exhibited encourages an even further promising future for AlGaN/GaN heterostructure devices. High electron mobility transistors (HEMTs) are becoming common place device structures in applicable fields, such as, 5 GHz and 6+ GHz RF technology and radar systems, with the potential to replace travelling wave vacuum tubes (TWT) technology. Field Plates (FP) are implemented with these structures to improve breakdown voltage (BV) by reshaping the electric field. Superjunction (SJ) and super-heterojunction (SHJ) theory is growing rapidly due to its advancements in BV and advanced electric field redistribution. A unique normally-on GaN/AlGaN/GaN lateral SHJ HEMT is proposed in this work. A p-type GaN SHJ structure with an ohmic Ni-Electrode electrically grounded to the source contact is introduced, along with a SJ charge balance between the P-GaN region and interfacial delta-doping at the upper U-GaN/AlGaN heterointerface. Silvaco TCAD simulation is used to examine the DC and RF characteristics under a Class A amplifier configuration. Data indicates SHJ region features improved uniform redistribution of electric fields over FPs. A decrease in switching performance with increase in frequency due to low mobility holes while switching is observed. Class-A operation of the device as it stands is limited to 1 GHz frequency. 10 GHz results show a PAE limitation of 25% due to low mobility holes. There appears to be an anomalous accumulation of holes in the i-GaN region, most significantly at 10 GHz. Future work must be completed to gain further insight on the source of the i-GaN holes. Current theories suggest possible simulation anomaly.