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Photoreflectance Probing of Below Gap States in Gan/Algan High Electron Mobility Transitor Structures

Published online by Cambridge University Press:  11 February 2011

D. K. Gaskill ,
O. J. Glembocki ,
B. Peres ,
R. Henry ,
D. Koleske  and
A. Wickenden
D. K. Gaskill
Affiliation:
Naval Research Laboratory, Washington, D.C. 20375
O. J. Glembocki
Affiliation:
Naval Research Laboratory, Washington, D.C. 20375
B. Peres
Affiliation:
Naval Research Laboratory, Washington, D.C. 20375
R. Henry
Affiliation:
Naval Research Laboratory, Washington, D.C. 20375
D. Koleske
Affiliation:
Naval Research Laboratory, Washington, D.C. 20375
A. Wickenden
Affiliation:
Naval Research Laboratory, Washington, D.C. 20375
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Abstract

Optical Impedence Spectroscopy of GaN/AlGaN high electron mobility transistor structures (HEMTs) using photoreflectance exhibit a photoreflectance lags – the component of the modulated reflectance out of phase with the chopper – ranging from 0.1 to 0.5. Photoreflectance was performed using below gap pumping on various samples. Samples that do exhibit appreciable photoreflectance lag for above gap pumping show significantly enhanced photoreflectance signals for below gap pumping. Yet, samples that do not exhibit appreciable photoreflectance lag for above gap pumping do not exhibit a signal for below gap pumping. This implies that the photoreflectance phase lag is due to mid-gap trap states. At least 2 types of traps are found, above and below about 2.5 eV. This result means that that photoreflectance can be used as a probe of HEMT device quality.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 743: Symposium L – GaN and Related Alloys , 2002 , L3.50
Copyright
Copyright © Materials Research Society 2003

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References

REFERENCES

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