Monolithic integration of a 10 µm cut-off wavelength InAs/GaSb type-II superlattice diode on GaAs platform.

At room temperature, a 10 µm cut-off wavelength coincides with an infrared spectral window and the peak emission of blackbody objects. We report a 10 µm cut-off wavelength InAs/GaSb T2SL p-i-n diode on a GaAs substrate with an intentional interfacial misfit (IMF) array between the GaSb buffer layer and GaAs substrate. Transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed that the heterostructure on GaSb-on-GaAs is epitaxial, single-crystalline but with a reduced material homogeneity, extended lattice defects and atomic segregation/intermixing in comparison to that on the GaSb substrate. Strain-induced degradation of the material quality is observed by temperature-dependent current-voltage measurements. The T2SL with the IMF array appears as a potentially effective route to mitigate the impact of the lattice mismatch once its fabrication is fully optimized for these systems, but additional strain compensating measures can enable a low cost, scalable manufacturing of focal plane arrays (FPA) for thermal imaging cameras for spectroscopy, dynamic scene projection, thermometry, and remote gas sensing.

Photoluminescence Characteristics of Zinc Blende InAs Nanowires.

A detailed understanding of the optical properties of self-catalysed (SC), zinc blende (ZB) dominant, nanowires (NWs) is crucial for the development of functional and impurity-free nanodevices. Despite the fact that SC InAs NWs mostly crystallize in the WZ/ZB phase, there are very limited reports on the photoluminescence (PL) properties of ZB InAs NWs. Here, we report on the PL properties of Molecular Beam Epitaxy grown, SC InAs NWs. The as-grown NWs exhibit a dominant band to band (BtB) peak associated with ZB, InAs with an emission energy of ~0.41 eV in good agreement with the band gap energy of ZB InAs and significantly lower than that of the wurtzite phase (~0.48 eV). The strong BtB peak persists to near room temperature with a distinct temperature-dependent red-shift and very narrow spectral linewidth of ~20 meV (10 K) which is much smaller than previously reported values. A narrowing in PL linewidth with increasing NWs diameter is correlated with a decline in the influence of surface defects resulting from an enlargement in NWs diameter. This study demonstrates the high optical property of SC InAs NWs which is compatible with the Si-complementary metal-oxide-semiconductor technology and paves the way for the monolithic integration of InAs NWs with Si in novel nanodevices.

Resonant Zener tunnelling via zero-dimensional states in a narrow gap diode.

Interband tunnelling of carriers through a forbidden energy gap, known as Zener tunnelling, is a phenomenon of fundamental and technological interest. Its experimental observation in the Esaki p-n semiconductor diode has led to the first demonstration and exploitation of quantum tunnelling in a condensed matter system. Here we demonstrate a new type of Zener tunnelling that involves the resonant transmission of electrons through zero-dimensional (0D) states. In our devices, a narrow quantum well of the mid-infrared (MIR) alloy In(AsN) is placed in the intrinsic (i) layer of a p-i-n diode. The incorporation of nitrogen in the quantum well creates 0D states that are localized on nanometer lengthscales. These levels provide intermediate states that act as "stepping stones" for electrons tunnelling across the diode and give rise to a negative differential resistance (NDR) that is weakly dependent on temperature. These electron transport properties have potential for the development of nanometre-scale non-linear components for electronics and MIR photonics.