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Microwave AlxGa1−xN/GaN Power HEMT's

Published online by Cambridge University Press:  17 March 2011

Lester F. Eastman
Lester F. Eastman*
Affiliation:
Electrical and Computer Engineering Cornell University 425 Phillips Hall Ithaca, NY 14853-5401
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Abstract

GaN in its hexagonal Wurtzite crystal has 3.4 eV bandgap and is capable of withstanding over 3 MV/cm electric field intensity. It is grown on either sapphire or SiC and the lattice mismatches cause threading dislocations. If it is grown along the c-axis on its Ga face, a thin pseudomorphic AlxGa1−xN barrier layer grown on top causes a substantial electrical polarization, which induces a substantial 2DEG in the GaN [1]. With x =.3 this 2 DEG is about 1 × 1013/cm2 without any doping impurities. The ∼ 109/cm2 threading dislocations accept electrons from the low density ambient donors, yielding very low net electron densities (< 1014/cm3) in the GaN buffer layer used as the HEMT channel [2]. The 2DEG electron mobility can be 1500-1700 cm2/V-s with ≥ 1 × 1013/cm2 electron sheet density. This 2DEG sheet density charge is less than the electrical polarization charge of 1.7 × 1013/cm2 for Al.3Ga.7N/GaN, due to some surface depletion and due to the fact that each dislocation traps ≥ 2 × 103 electrons. The design, processing, and measured performance of such undoped, polarization-induced HEMT's are presented below.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 639: Symposium G – GaN and Related Alloys-2000 , 2000 , G8.2
Copyright
Copyright © Materials Research Society 2001

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References

REFERENCES

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