Measurement of the hot electron mean free path and the momentum relaxation rate in GaN

We present a method for measuring the mean free path and extracting the momentum relaxation time of hot electrons in GaN using the hot electron transistor (HET). In this device, electrons are injected over a high energy emitter barrier into the base where they experience quasi-ballistic transport we...

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Bibliographic Details
Published in:Applied physics letters 2014-12, Vol.105 (26)
Main Authors: Suntrup, Donald J., Gupta, Geetak, Li, Haoran, Keller, Stacia, Mishra, Umesh K.
Format: Article
Language:English
Subjects:
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
ELECTRIC CURRENTS
ELECTRONIC STRUCTURE
ELECTRONS
GALLIUM NITRIDES
MEAN FREE PATH
PHONONS
RELAXATION TIME
SCATTERING
TRANSISTORS
VELOCITY
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Summary:We present a method for measuring the mean free path and extracting the momentum relaxation time of hot electrons in GaN using the hot electron transistor (HET). In this device, electrons are injected over a high energy emitter barrier into the base where they experience quasi-ballistic transport well above the conduction band edge. After traversing the base, high energy electrons either surmount the base-collector barrier and become collector current or reflect off the barrier and become base current. We fabricate HETs with various base thicknesses and measure the common emitter transfer ratio (α) for each device. The mean free path is extracted by fitting α to a decaying exponential as a function of base width and the relaxation time is computed using a suitable injection velocity. For devices with an injection energy of ∼1 eV, we measure a hot electron mean free path of 14 nm and calculate a momentum relaxation time of 16 fs. These values are in agreement with theoretical calculations where longitudinal optical phonon scattering is the dominant momentum relaxation mechanism.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4905367