Journal
JOURNAL OF APPLIED PHYSICS
Volume 104, Issue 12, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.3033140
Keywords
doping profiles; gallium arsenide; high-speed optical techniques; III-V semiconductors; molecular beam epitaxial growth; phonons; semiconductor epitaxial layers; ultrasonic effects
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Funding
- DFG [SFB 767]
- Ministry of Science, Research and the Arts
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The doping profile in different n-doped GaAs homoepitaxial structures grown by molecular beam epitaxy is investigated in the time domain by employing a laser based picosecond ultrasound technique in a contactless and noninvasive way. Experiments based on asynchronous optical sampling employ two femtosecond lasers, which allow us to detect changes in the optical reflectivity over a 1 ns time delay with a signal-to-noise ratio of 10(7) and 100 fs time resolution in < 1 min of acquisition time. We show that the doping profile with doping densities of the order of 10(18) cm(-3) can be detected with picosecond ultrasound, although there is no difference in the acoustic properties of the doped and undoped region. The detection mechanism is based on a different sensitivity function for a coherent strain pulse in the doped and undoped regions. These results are corroborated by experiments at room temperature and 10 K.
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