10 research outputs found
Superconductivity in hyperdoped Ge by molecular beam epitaxy
Superconducting germanium films are an intriguing material for possible
applications in fields such as cryogenic electronics and quantum bits.
Recently, there has been great deal of progress in hyperdoping of Ga doped Ge
using ion implantation. The thin film growths would be advantageous allowing
homoepitaxy of doped and undoped Ge films opening possibilities for vertical
Josephson junctions. Here, we present our studies on the growth of one layer of
hyperdoped superconducting germanium thin film via molecular beam epitaxy. We
observe a fragile superconducting phase which is extremely sensitive to
processing conditions and can easily phase-segregate, forming a percolated
network of pure gallium metal. By suppressing phase segregation through
temperature control we find a superconducting phase that is unique and appears
coherent to the underlying Ge substrate
Influence of a Bi surfactant on Sb incorporation in InAsSb alloys
The influence of using a Bi surfactant during the growth of InAsSb on the composition was examined, and it was found that increasing Bi flux on the surface during growth inhibits the incorporation of Sb. Analysis of the data via a kinetic model of anion incorporation shows that surface Bi acts as a catalyst for InAs formation, thus inhibiting Sb incorporation
Engineering Dirac Materials: Metamorphic InAs<sub>1–<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1–<i>y</i></sub>Sb<sub><i>y</i></sub> Superlattices with Ultralow Bandgap
Quasiparticles
with Dirac-type dispersion can be observed in nearly
gapless bulk semiconductors alloys in which the bandgap is controlled
through the material composition. We demonstrate that the Dirac dispersion
can be realized in short-period InAs<sub>1–<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1–<i>y</i></sub>Sb<sub><i>y</i></sub> metamorphic superlattices with
the bandgap tuned to zero by adjusting the superlattice period and
layer strain. The new material has anisotropic carrier dispersion:
the carrier energy associated with the in-plane motion is proportional
to the wave vector and characterized by the Fermi velocity <i>v</i><sub>F</sub>, and the dispersion corresponding to the motion
in the growth direction is quadratic. Experimental estimate of the
Fermi velocity gives <i>v</i><sub>F</sub> = 6.7 × 10<sup>5</sup> m/s. Remarkably, the Fermi velocity in this system can be
controlled by varying the overlap between electron and hole states
in the superlattice. Extreme design flexibility makes the short-period
metamorphic InAs<sub>1–<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1–<i>y</i></sub>Sb<sub><i>y</i></sub> superlattice a new prospective platform
for studying the effects of charge-carrier chirality and topologically
nontrivial states in structures with the inverted bandgaps