Performance Enhancement of Microwave GaN HEMTs Without an AlN-Exclusion Layer Using an Optimized AlGaN/GaN Interface Growth Process
Journal article, 2016

The impact of the sharpness of the AlGaN/GaN interface in high-electron mobility transistors (HEMTs) is investigated. Two structures, one with an optimized AlGaN/GaN interface and another with an unoptimized, were grown using hot-wall metal-organic chemical vapor deposition. The structure with optimized sharpness of the interface shows electron mobility of 1760 cm(2)/V . s as compared with 1660 cm(2)/V . s for the nonoptimized interface. Gated Hall measurements indicate that the sharper interface maintains higher mobility when the electrons are close to the interface compared with the nonoptimized structure, indicating less scattering due to alloy disorder and interface roughness. HEMTs were processed and evaluated. The higher mobility manifests as lower parasitic resistance yielding a better dc and high-frequency performance. A small-signal equivalent model is extracted. The results indicate a lower electron penetration into the buffer in the optimized sample. Pulsed-IV measurements imply that the sharper interface provides less dispersive effects at large drain biases. We speculate that the mobility enhancement seen AlGaN/AlN/GaN structures compared with the AlGaN/GaN case is not only related to the larger conduction band offset but also due to a more welldefined interface minimizing scattering due to alloy disorder and interface roughness.

AlGaN/GaN interface

interface sharpness

GaN high-electron mobility transistor (HEMT)

Author

Johan Bergsten

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

J. T. Chen

Linköping University

Sebastian Gustafsson

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

Anna Malmros

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

Urban Forsberg

Linköping University

Mattias Thorsell

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

E. Janzen

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

Niklas Rorsman

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

IEEE Transactions on Electron Devices

0018-9383 (ISSN)

Vol. 63 1 333-338

Subject Categories

Electrical Engineering, Electronic Engineering, Information Engineering

DOI

10.1109/ted.2015.2501838

More information

Latest update

7/27/2018