Two dimensional electron gas in GaN heterojunction field effect transistors structures with AlN spacer

Qian Fan, Jacob H. Leach, Jinqiao Xie, Umit Ozgur, Hadis Morkoç, L. Zhou, David Smith

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

Near lattice matched Al 0.81In 0.19N/GaN heterojunction structures are compared with conventional Al 0.3Ga 0.7N/GaN heterojunctions in terms of the sheet density and mobility and their dependence on barrier and spacer layer parameters. With the insertion of an AlN spacer, the mobility of both structures is improved dramatically. Self-consistent solution of Poisson-Schrödinger equations was developed in order to determine the band structure and carrier distribution in these GaN based heterostructures in an effort to gain insight into the experimental observations. Surface donor states were included to account for the origin of electrons in 2DEG, which is treated as charge neutralization conditions in the simulation. Also the change in the piezoelectric polarization due to the electromechanical coupling effect, and shift of band gap caused by uniaxial strain were both included in the calculations. The calculated sheet density is close to the measured values, especially for the AlGaN samples investigated, but a notable difference was noted in the AlInN cases. The discrepancy is confirmed to be caused by the existence of a Ga-rich layer on the top of AlN spacer during the growth interruption, which can split the 2DEG into two channels with different mobilities and lower the overall sheet density. When the modifications made necessary by this GaN layer are taken into account in our model for the AlInN barrier case, the calculations match with the experimental data. When the spacer thickness increase from 0.3 to 3 nm, the total sheet density was found to slightly increase experimentally, which agreed with the theoretical prediction.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
Volume7216
DOIs
StatePublished - 2009
EventGallium Nitride Materials and Devices IV - San Jose, CA, United States
Duration: Jan 26 2009Jan 29 2009

Other

OtherGallium Nitride Materials and Devices IV
CountryUnited States
CitySan Jose, CA
Period1/26/091/29/09

ASJC Scopus subject areas

  • Applied Mathematics
  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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    Fan, Q., Leach, J. H., Xie, J., Ozgur, U., Morkoç, H., Zhou, L., & Smith, D. (2009). Two dimensional electron gas in GaN heterojunction field effect transistors structures with AlN spacer. In Proceedings of SPIE - The International Society for Optical Engineering (Vol. 7216). [72162N] https://doi.org/10.1117/12.811678