This work investigates the electronic band structures of bulk Ge 1-x Sn x alloys using the empirical pseudopotential method (EPM) for Sn composition x varying from 0 to 0.2. The adjustable form factors of EPM were tuned in order to reproduce the band features that agree well with the reported experimental data. Based on the adjusted pseudopotential form factors, the band structures of Ge 1-x Sn x alloys were calculated along high symmetry lines in the Brillouin zone. The effective masses at the band edges were extracted by using a parabolic line fit. The bowing parameters of hole and electron effective masses were then derived by fitting the effective mass at different Sn compositions by a quadratic polynomial. The hole and electron effective mass were examined for bulk Ge 1-x Sn x alloys along specific directions or orientations on various crystal planes. In addition, employing the effective-mass Hamiltonian for diamond semiconductor, band edge dispersion at the C-point calculated by 8-band k.p. method was fitted to that obtained from EPM approach. The Luttinger-like parameters were also derived for Ge 1-x Sn x alloys. They were obtained by adjusting the effective-mass parameters of k.p method to fit the k.p band structure to that of the EPM. These effective masses and derived Luttinger parameters are useful for the design of optical and electronic devices based on Ge 1-x Sn x alloys. V C 2012 American Institute of Physics.

We report the first realization of fully-released and relaxed Ge1-xSnx structures on Ge substrate. The coefficients of Raman peak shift a and b due to the alloy disorder and strain, respectively, were experimentally obtained for Ge1-xSnx. In addition, to lower the Sn composition needed to achieve direct bandgap Ge1-xSnx alloys and also to realize channel materials with higher electron mobility, uniaxially tensile strained Ge1-xSnx patterns were fabricated. Large tensile strain (>1%) was detected in the patterned Ge1-xSnx lines. Such tensile-strained Ge1-xSnx structures could enable the realization of Group-IV optoelectronic devices and high mobility n-channel transistors.

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In-memory computing featuring a radical departure from the von Neumann architecture is promising to substantially reduce the energy and time consumption for data-intensive computation. With the increasing challenges facing silicon complementary metal-oxide-semiconductor (CMOS) technology, developing in-memory computing hardware would require a different platform to deliver significantly enhanced functionalities at the material and device level. Here, we explore a dual-gate two-dimensional ferroelectric field-effect transistor (2D FeFET) as a basic device to form both nonvolatile logic gates and artificial synapses, addressing in-memory computing simultaneously in digital and analog spaces. Through diversifying the electrostatic behaviors in 2D transistors with the dual-ferroelectric-coupling effect, rich logic functionalities including linear (AND, OR) and nonlinear (XNOR) gates were obtained in unipolar (MoS2) and ambipolar (MoTe2) FeFETs. Combining both types of 2D FeFETs in a heterogeneous platform, an important computation circuit, i.e., a half-adder, was successfully constructed with an area-efficient two-transistor structure. Furthermore, with the same device structure, several key synaptic functions are shown at the device level, and an artificial neural network is simulated at the system level, manifesting its potential for neuromorphic computing. These findings highlight the prospects of dual-gate 2D FeFETs for the development of multifunctional in-memory computing hardware capable of both digital and analog computation.