Burcu Ozden’s research focuses on revealing and understanding the basic physics involved exciton-photon transfer and electric transport properties of polariton condensates. Her research is highly experimental. She fabricates her own multiple quantum well microcavities at Nanotechnology Laboratories of at University of Pittsburgh and Carnegie Mellon University. She then create excitons or polaritons in semiconductor samples at liquid helium temperatures via an intense, ultrafast (picosecond or femtosecond) laser pulse and then investigates the transport properties of these quasiparticles. Moreover, she uses software tools to understand the underlying physics. She also collaborate with theorists to answer fundamental questions about exciton and polariton condensates. Her research is funded by Army Research Office.
Burcu Ozden
Penn State Abington
Research
- Microcavity Polaritons
- Wide Band Gap Semiconductors
- Optoelectronic Characterization of III-V Materials
- Radiation Effect
Research Projects
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We create excitons or polaritons in semiconductor samples at liquid helium temperatures via an intense, ultrafast (picosecond or femtosecond) laser pulse while applying external electric field, and then examine the evolution of their momentum distribution and spatial distribution by detecting the light they emit. In this research we aim to achieve separate electrical contacts at di erent positions on a quantum well boundary, and to separate quantum wells, when the wells are placed inside a microcavity in which an exciton-polariton condensate is produced by optical pumping. We predict that the electrical current couples to the condensate through quasiparticle-exciton and exciton photon transfer mechanisms that are similar to the quasiparticle-condensate mechanisms associated with Andreev scattering in superconductors and spin-transfer torques in magnetic systems. These novel phenomena may lead to new types of electro-optical like optical communications and memory devices.This would revolutionize technology in the way the electronic transistor did 50 years ago
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A simple and novel spectroscopic photo I–V method of diagnosing the
homogeneity of electrically-active defect distribution in the large area
AlGaN/GaN HEMT (high electron mobility transistor) epi-structure
grown on 6-inch silicon wafers is reported. It is of utmost importance
to produce the HEMT epi-structure electrically homogeneous across
the wafer if devices with uniform electrical characteristics are to be
constructed. AlGaN/GaN HEMT epi structures were grown on a
silicon substrate via metal–organic chemical vapour deposition. An
array of circular semi-transparent Ni Schottky contacts was prepared
on top of the diced AlGaN/GaN HEMT structure substrates, which
were selected from different locations of the 6-inch wafer. The information
of the electrical homogeneity across the wafer was elucidated
from the spectral dependences of the I–V characteristics collected
from different locations of the AlGaN/GaN HEMT wafer. It is successfully
demonstrated that the proposed spectroscopic photo I–V measurement
technique can be employed to diagnose electrical homogeneity of
the electrically-active defect distribution in the AlGaN/GaN HEMT epi
structure constructed on Si with minimum sample preparation steps. -
We have demonstrated that the depth-dependent defect distribution of the deep level traps in the
AlGaN/GaN high electron mobility transistor (HEMT) epi-structures can be analyzed by using the
depth-resolved ultra-violet (UV) spectroscopic photo current-voltage (IV) (DR-UV-SPIV). It is of
great importance to analyze deep level defects in the AlGaN/GaN HEMT structure, since it is
recognized that deep level defects are the main source for causing current collapse phenomena
leading to reduced device reliability. The AlGaN/GaN HEMT epi-layers were grown on a 6 in.
Si wafer by metal-organic chemical vapor deposition. The DR-UV-SPIV measurement was
performed using a monochromatized UV light illumination from a Xe lamp. The key strength of
the DR-UV-SPIV is its ability to provide information on the depth-dependent electrically active
defect distribution along the epi-layer growth direction. The DR-UV-SPIV data showed variations
in the depth-dependent defect distribution across the wafer. As a result, rapid feedback on the
depth-dependent electrical homogeneity of the electrically active defect distribution in the AlGaN/
GaN HEMT epi-structure grown on a Si wafer with minimal sample preparation can be elucidated
from the DR-UV-SPIV in combination with our previously demonstrated spectroscopic photo-IV
measurement with the sub-bandgap excitation. -
Time-resolved photocurrent (TRPC) spectroscopy with a variable-wavelength sub-bandgap light excitation was used to study the dynamics of the decaying photocurrent generated in the heterostructures of the AlGaN/GaN high electron mobility transistors (HEMTs) layers. In AlGaN/GaN HEMTs, reliability of the device is degraded due to the prevalence of current collapse. It is recognized that electrically active deep level defects at the surface/interfaces and the bulk in the HEMTs layers can contribute to the unwanted current collapse effect. Therefore, it is of great importance to analyze the deep level defects if the reliability of the HEMTs device is to be improved. In this research, TRPC spectroscopy was used to elucidate the origin and nature of the deep level defects by analyzing the time evolution of the photocurrent decay excited at different wavelengths of light. The two devices that show similar characteristics for wavelength-dependency on photocurrent generation were chosen, and TRPC spectroscopy was conducted on these devices. Although the two samples show similar characteristics for the wavelength-dependency on photocurrent generation, they exhibited dissimilar time-dependent photocurrent decay dynamics. This implies that TRPC spectroscopy can be used to distinguish the traps which have different origins but have the same de-trapping energy.