Over the past several years, the inherent scaling limitations of silicon (Si) electron devices have fuelled the exploration of alternative semiconductors, with high carrier mobility, to further enhance device performance. In particular, compound semiconductors heterogeneously integrated on Si substrates have been actively studied: such devices combine the high mobility of III-V semiconductors and the well established, low-cost processing of Si technology. This integration, however, presents significant challenges. Conventionally, heteroepitaxial growth of complex multilayers on Si has been explored-but besides complexity, high defect densities and junction leakage currents present limitations in this approach. Motivated by this challenge, here we use an epitaxial transfer method for the integration of ultrathin layers of single-crystal InAs on Si/SiO(2) substrates. As a parallel with silicon-on-insulator (SOI) technology, we use 'XOI' to represent our compound semiconductor-on-insulator platform. Through experiments and simulation, the electrical properties of InAs XOI transistors are explored, elucidating the critical role of quantum confinement in the transport properties of ultrathin XOI layers. Importantly, a high-quality InAs/dielectric interface is obtained by the use of a novel thermally grown interfacial InAsO(x) layer (~1 nm thick). The fabricated field-effect transistors exhibit a peak transconductance of ~1.6 mS µm(-1) at a drain-source voltage of 0.5 V, with an on/off current ratio of greater than 10,000.

The authors report on a type-II InAs∕GaSb strained layer superlattice (SLS) photodetector using an nBn design that can be used to eliminate both Shockley-Read-Hall generation currents and surface recombination currents, leading to a higher operating temperature. We present such a SLS based structure with a cutoff wavelength of 5.2μm at room temperature. Processed devices exhibited a quantum efficiency around 18%, and a shot-noise-limited specific detectivity ∼109Jones at 4.5μm and 300K, which are comparable to the state of the art values reported for p-i-n photodiodes based on strained layer superlattices.

As of yet, III-V p-type field-effect transistors (p-FETs) on Si have not been reported, due partly to materials and processing challenges, presenting an important bottleneck in the development of complementary III-V electronics. Here, we report the first high-mobility III-V p-FET on Si, enabled by the epitaxial layer transfer of InGaSb heterostructures with nanoscale thicknesses. Importantly, the use of ultrathin (thickness, ~2.5 nm) InAs cladding layers results in drastic performance enhancements arising from (i) surface passivation of the InGaSb channel, (ii) mobility enhancement due to the confinement of holes in InGaSb, and (iii) low-resistance, dopant-free contacts due to the type III band alignment of the heterojunction. The fabricated p-FETs display a peak effective mobility of ~820 cm(2)/(V s) for holes with a subthreshold swing of ~130 mV/decade. The results present an important advance in the field of III-V electronics.

The optical absorption properties of free-standing InAs nanomembranes of thicknesses ranging from 3 nm to 19 nm are investigated by Fourier transform infrared spectroscopy. Stepwise absorption at room temperature is observed, arising from the interband transitions between the subbands of 2D InAs nanomembranes. Interestingly, the absorptance associated with each step is measured to be ∼1.6%, independent of thickness of the membranes. The experimental results are consistent with the theoretically predicted absorptance quantum, A Q = πα/n c for each set of interband transitions in a 2D semiconductor, where α is the fine structure constant and n c is an optical local field correction factor. Absorptance quantization appears to be universal in 2D systems including III-V quantum wells and graphene.T he optical properties of heterostructure quantum wells (QWs) have been extensively studied since the 1970s, in GaAs/ AlGaAs (1), GaInAs/AlInAs (2, 3), InGaAs/InP (4), and HgCdTe/ CdTe (5). Here we do a careful quantitative examination of the intrinsic absorption properties of free-standing 2D semiconductor thin films, which has previously been done only for layered structures, such as MoS 2 (6). (The criterion of real two-dimensionality is that the material thickness be smaller than the electron Bohr radius.)Previous work has shown that graphene, a 2D semimetal, has a universal value of light absorption, namely πα, where α is the fine structure constant (7). Here, we use free-standing InAs membranes with exceptionally small thickness as a model material system to accurately probe the absorption properties of 2D semiconductors as a function of thickness. We demonstrate that the magnitude of the light absorption is an integer product of a quantum of absorptance. Specifically, each set of interband transitions between the 2D subbands results in a quantum unit of absorptance of A Q ∼ πα/n c , where n c is the optical local field correction factor. The total absorptance for the first several sets of interband transitions is simply given as A = MA Q , where M is the integer number of allowed transitions for a given photon energy. The result here appears to be universal, except for small correction factors associated with higher bands.Recently, there has been a high level of interest in exploring the fundamental science (6-10) and associated devices (11-20) of free-standing (i.e., attached to a substrate by van der Waals or other weak forces) 2D semiconductors. In one example system, InAs quantum membranes (QMs) with adjustable thicknesses down to a few atomic layers have been realized by a layer transfer process onto a user-defined substrate (12). The approach enables the direct optical absorption studies of fully relaxed (i.e., unstrained) (21) 2D III-V semiconductors by using transparent substrates, without the constraints of the original growth substrate (10). Here, we use InAs membranes of thickness L z ∼ 3-19nm on CaF 2 support substrates as a model material system for examining the absorption properties of 2D semiconduc...

Nanoscale size effects drastically alter the fundamental properties of semiconductors. Here, we investigate the dominant role of quantum confinement in the field-effect device properties of free-standing InAs nanomembranes with varied thicknesses of 5-50 nm. First, optical absorption studies are performed by transferring InAs "quantum membranes" (QMs) onto transparent substrates, from which the quantized sub-bands are directly visualized. These sub-bands determine the contact resistance of the system with the experimental values consistent with the expected number of quantum transport modes available for a given thickness. Finally, the effective electron mobility of InAs QMs is shown to exhibit anomalous field and thickness dependences that are in distinct contrast to the conventional MOSFET models, arising from the strong quantum confinement of carriers. The results provide an important advance toward establishing the fundamental device physics of two-dimensional semiconductors.