In this work, a study of two different types of current aperture vertical electron transistor (CAVET) with ion-implanted blocking layer are presented. The device fabrication and performance limitation of a CAVET with a dielectric gate is discussed, and the breakdown limiting structure is evaluated using on-wafer test structures. The gate dielectric limited the device breakdown to 50V, while the blocking layer was able to withstand over 400V. To improve the device performance, an alternative CAVET structure with a p-GaN gate instead of dielectric is designed and realized. The pGaN gated CAVET structure increased the breakdown voltage to over 400V. Measurement of test structures on the wafer showed the breakdown was limited by the blocking layer instead of the gate p-n junction.
High quality germanium doped β-Ga2O3 epitaxial film was grown by PMBE technique and fabricated into a vertical type Schottky photodiode with a Pt/nGa2O3/n+Ga2O3(010) structure. The photodiode exhibited excellent rectifying characteristics with a turn on voltage ~ 1V and near zero bias leakage current ~ 100 fA. The photoresponse measurement showed a true solar blind sensitivity with cutoff wavelength ~260 nm and an out of band rejection ratio of ~104. A maximum responsivity of 0.09 A/W at 230 nm was measured at zero bias, corresponding to an external quantum efficiency of ~52 %. The time response of the photovoltaic diode is in the millisecond range and has no long-time decay component which is very common in the MSM photoconductive wide bandgap devices. The photodiode performance remains stable up to 300°C, suggesting its potential use for high temperature applications.
The interaction of quantum radiation and a two-level atom is described in the context through the Jaynes-Cummings-Paul Hamiltonian which is obtained through Heisenberg's interaction picture of the Atom-Radiation Hamiltonian. We
argue that such a transformation is not mathematically exact in case of ultrastrong coupling, where the coupling rate is
comparable to the transition frequency, and leads to erroneous results. In addition, we introduce an exact mathematical
solution to calculate optical spectrum of this system.
A theory is presented for the quantum radiation emitted from a single exciton in a quantum dot. We assume that the
quantum dot is in strong coupling to a slab photonic crystal cavity. A dielectric function of spatial coordinates is used to
explain the effects of the macroscopic medium. It has been proved that the electric field in such a medium can be
described using the so-called K-function. We derive a formula for obtaining the frequency spectrum, and present an
analytical result for the optical spectrum, which is dependent on the K-function. We also have considered a slab photonic
crystal configuration with hexagonal structure containing a cavity to evaluate the frequency spectrum in such a medium.
FDTD method has been used to calculate the generalized-transverse green function and the K-function everywhere in the
medium.
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