An infrared camera based on a 256×256 focal plane array (FPA) for the second atmospheric window (3–5 μm) has been realized
for the first time with InAs/GaSb short period superlattices (SLs). The SL detector structure with a broken gap type-II band
alignment was grown by molecular beam epitaxy on GaSb substrates. Effective bandgap and strain in the superlattice were adjusted
by varying the thickness of the InAs and GaSb layers and the controlled formation of InSb-like bonds at the interfaces. The
FPAs were processed in a full wafer process using optical lithography, chemical-assisted ion beam etching, and conventional
metallization technology. The FPAs were flip-chip bonded using indium solder bumps with a read-out integrated circuit and
mounted into an integrated detector cooler assembly. The FPAs with a cut-off wavelength of 5.4 μm exhibit quantum efficiencies
of 30% and detectivity values exceeding 1013 Jones at T=77 K. A noise equivalent temperature difference (NETD) of 11.1 mK was measured for an integration time of 5 ms
using f/2 optics. The NETD scales inversely proportional to the square root of the integration time between 5 ms and 1 ms,
revealing background limited performance. Excellent thermal images with low NETD values and a very good modulation transfer
function demonstrate the high potential of this material system for the fabrication of future thermal imaging systems. 相似文献
We report on investigation of the spin dynamics in InAs and InSb films grown on GaAs at a temperature range from 77 K to 290 K.
For both materials, the large lattice mismatch with the GaAs substrate results in the formation of an interface accumulation
layer with a large defect concentration, which strongly affects the spin relaxation in these areas. Moreover, the native surface
defect in the InAs films resulted in an additional charge accumulation layer with high conductivity, but very short spin lifetime.
In contrast, in InSb layers, the surface states introduce a depletion region. We have correlated the spin relaxation with
a multi-layer analysis of the transport properties, and find that in a 1 μm thick InAs film, approximately 70% of the total
current flows through the interface and surface accumulation layers, which have sub-picosecond lifetimes, whereas in InSb
films of the same thickness, the semiconducting layer carries more than 90% of the total current, and the spin lifetime in
the accumulation layer is only slightly less than that of the central semiconducting layer. We suggest that InSb could be
a more attractive candidate for spintronic applications than InAs. 相似文献
Heterostructures for InAs-channel high-electron-mobility transistors (HEMTs) were investigated. Reactive AlSb buffer and barrier
layers were replaced by more stable Al0.7Ga0.3Sb and In0.2Al0.8Sb alloys. The distance between the gate and the channel was reduced to 7–13 nm to allow good aspect ratios for very short
gate lengths. In addition, n+-InAs caps were successfully deposited on the In0.2Al0.8Sb upper barrier allowing for low sheet resistance with relatively low sheet carrier density in the channel. These advances
are expected to result in InAs-channel HEMTs with enhanced microwave performance and better reliability. 相似文献
We report the direct observation of coupling between a single self-assembled InAs quantum dot and a wetting layer, based on strong diamagnetic shifts of many-body exciton states using magneto-photoluminescence spectroscopy. An extremely large positive diamagnetic coefficient is observed when an electron in the wetting layer combines with a hole in the quantum dot; the coefficient is nearly one order of magnitude larger than that of the exciton states confined in the quantum dots. Recombination of electrons with holes in a quantum dot of the coupled system leads to an unusual negative diamagnetic effect, which is five times stronger than that in a pure quantum dot system. This effect can be attributed to the expansion of the wavefunction of remaining electrons in the wetting layer or the spread of electrons in the excited states of the quantum dot to the wetting layer after recombination. In this case, the wavefunction extent of the final states in the quantum dot plane is much larger than that of the initial states because of the absence of holes in the quantum dot to attract electrons. The properties of emitted photons that depend on the large electron wavefunction extents in the wetting layer indicate that the coupling occurs between systems of different dimensionality, which is also verified from the results obtained by applying a magnetic field in different configurations. This study paves a new way to observe hybrid states with zero- and two-dimensional structures, which could be useful for investigating the Kondo physics and implementing spin-based solid-state quantum information processing.