In this study, electronic properties of field-effect transistors (FETs) fabricated from exfoliated MoTe2 single crystals are investigated as a function of channel thickness. The conductivity type in FETs gradually changes from n-type for thick MoTe2 layers (above ≈ 65 nm) to ambipolar behavior for intermediate MoTe2 thickness (between ≈ 60 and 15 nm) to ptype for thin layers (below ≈ 10 nm). The n-type behavior in quasi-bulk MoTe2 is attributed to doping with chlorine atoms from the TeCl4 transport agent used for the chemical vapor transport (CVT) growth of MoTe2. The change in polarity sign with decreasing channel thickness may be associated with increasing role of surface states in ultra-thin layers, which in turn influence carrier concentration and dynamics in the channel due to modulation of Schottky barrier height and band-bending at the metal/semiconductor interface.
We have demonstrated flexible packaging and integration of CMOS IC chips with PDMS microfluidics. Microfluidic channels are used to deliver both liquid samples and liquid metals to the CMOS die. The liquid metals are used to realize electrical interconnects to the CMOS chip. As a demonstration we integrated a CMOS magnetic sensor die and matched PDMS microfluidic channels in a flexible package. The packaged system is fully functional under 3cm bending radius. The flexible integration of CMOS ICs with microfluidics enables previously unavailable flexible CMOS electronic systems with fluidic manipulation capabilities, which hold great potential for wearable health monitoring, point-of-care diagnostics and environmental sensing.
Investigations of the static characteristics, responsivity, internal noises, and detectivity of the forward biased p-i-n
photodetectors made on wide bandgap compensated semiconductors operating in double injection regime are presented.
Noise related calculations are performed by utilizing "Impedance Field Method". Numerical simulations are made
assessing 4H-SiC and GaN biased p-i-n photodiodes noise related characteristics. It is shown that forward biased p-i-n
photodiodes have low level of thermal and generation-recombination noises and high values of sensitivity and detectivity
at the room temperature.
In this paper we show an approach to couple two stochastic processes to describe the dynamics of independent carriers in
semiconductor devices: the launch time of carriers from the contacts is described by independent Poisson launch
processes, and the stochastic motion of carriers due to scattering inside the device is described by inhomogeneous
Poisson type Markov processes according to the semiclassical transport theory. The coupling of the Poisson type
stochastic launch process to the semiclassical dynamics will be shown, and the resulting Ohmic contact boundary
conditions will be derived. For proof of concept, an expression for the autocovariance for terminal current noise for one
point contact will be shown which can be easily extended to a real semiconductor device with multiple contacts.
Process of the origin and relaxation of the fluctuation of distribution function of conduction electrons in space-homogenous and non-degenerate equilibrium semiconductors is discussed. The fluctuations of electron distribution function, formed as result of the internal fluctuations of the phonon system, are studied. The physical mechanisms of the origin and following slow (diffusion) damping of the equilibrium fluctuations of the electron and phonon distribution functions are represented. It is shown that in low frequency region the Fourier-component of distribution function fluctuations of predominantly long wavelength electrons and phonons are depends on frequency by law ω-1/2.
The two main causes of origin of the mobility fluctuation of the electrons in homogeneous, unlimited, and non-degenerated semiconductors are discussed. It is shown that the mobility fluctuation is conditioned by the symmetric component of the fluctuation of the distribution function, i.e. by the fluctuations of the conduction electrons energy. On the base of the developed quasi-classical model the spectrum of electrons lattice mobility fluctuations is calculated. In the frequency wide variation range it has 1/f form.