28 research outputs found
Two-dimensional electron gas formation in undoped In[0.75]Ga[0.25]As/In[0.75]Al[0.25]As quantum wells
We report on the achievement of a two-dimensional electron gas in completely
undoped In[0.75]Al[0.25]As/In[0.75]Ga[0.25]As metamorphic quantum wells. Using
these structures we were able to reduce the carrier density, with respect to
reported values in similar modulation-doped structures. We found experimentally
that the electronic charge in the quantum well is likely due to a deep-level
donor state in the In[0.75]Al[0.25]As barrier band gap, whose energy lies
within the In[0.75]Ga[0.25]As/In[0.75]Al[0.25]As conduction band discontinuity.
This result is further confirmed through a Poisson-Schroedinger simulation of
the two-dimensional electron gas structure.Comment: 17 pages, 6 figures, to be published in J. Vac. Sci. Technol.
Enhancement of field generation via maximal atomic coherence prepared by fast adiabatic passage in Rb vapor
We have experimentally demonstrated the enhancement of coherent Raman
scattering in Rb atomic vapor by exciting atomic coherence with fractional
stimulated Raman adiabatic passage. Experimental results are in good agreement
with numerical simulations. The results support the possibility of increasing
the sensitivity of CARS by preparing atomic or molecular coherence using short
pulses