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- CMOS-Schaltung (2)
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- Power generation; Logic Gates; Gallium nitride; Attenuators; HEMTs; Printed circuits; Power measurement; Limit; GaN; HEMT; ruggedness; low noise amplifier (LNA); receiver (2)
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A novel setup allowing for recovery time measurement of robust GaN LNA is presented in this paper. The setup is based on an PNA-X vector network analyzer and allows for the characterization of the LNA's small-signal gain, while it also monitors overdrive pulse power and reflected pulse power. The system setup and operation is shown in detail. As an example, two different GaN LNAs were measured in order to validate the test setup.
Rugged GaN HEMT low-noise amplifiers are well established, but the common concept of achieving ruggedness by applying the gate supply voltage through a high ohmic resistance might not be sufficient in addition to control the maximum output power. This paper shifts the focus to the protection of subsequent stages and proposes a circuit concept based on an output attenuator and an adaptive drain supply. It is shown that the concept implementation provides an attenuation of up to 28dB under input overdrive condition while leaving small-signal noise Figure unaffected.
Rugged GaN HEMT low-noise amplifiers are well established, but the common concept of achieving ruggedness by applying the gate supply voltage through a high ohmic resistance might not be sufficient in addition to control the maximum output power. This paper shifts the focus to the protection of subsequent stages and proposes a circuit concept based on an output attenuator and an adaptive drain supply. It is shown that the concept implementation provides an attenuation of up to 28 dB under input overdrive condition while leaving small-signal noise figure unaffected.
Experimental observations and quantum mechanical device simulations point to different electronic properties of dislocations in silicon and germanium. The experimental data suggest a supermetallic behavior of the dislocations in Si and thus the high strain in the dislocation core is thought to cause the confinement of the charge carriers, which leads to the formation of a 1D electron gas along a dislocation (quantum wire). The resulting significant increase in the electron concentration corresponds to a marked increase in the drain current of metal–oxide–semiconductor field‐effect transistor (MOSFET). The specific resistance of an individual dislocation in Ge is about nine orders of magnitude higher than for a dislocation in Si. The experimental measurements of the strain in dislocation cores in Ge are still missing. Based on the band structure data, the generation of a strain equivalent to that of the dislocation cores in Si appears to be very challenging because of the transition from an indirect into a direct semiconductor with about tenfold lower strain levels. The lower strain in the dislocation core in germanium may not support the carrier confinement as proposed for the dislocation core of silicon, and consequently 1D electron gases are not expected to form along the dislocations in Ge.
Local electronic states of regular dislocation networks produced by n- and p-type silicon wafer bonding with different screw dislocation density were studied with deep-level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS). A drastic sadden changes of the electric level spectrum with increasing of dislocation density from two shallow bands located near the edges of valence and conduction bands towards two deep bands with energy positions about Ec - (0.22-0.26) eV and Ev + (0.4-0.53) eV were found. The origin of the electric level spectrum changes is ascribed to the changes of dislocation core structure from dissociated to perfect ones that occur when interdislocation distances became comparable with the dislocation equilibrium dissociation width. The obtained results correlate well with the results of recent studies of recombination activity of grain boundaries in mc-Si.
For mono-crystalline Ge the indirect luminescence intensity declines upon growing temperature from 80 to 300 K, whereas for dislocated Ge structures the opposite behavior occurs. These findings are comparable to earlier observations on Si. The drop of the luminescence in dislocated material upon lowering temperature was attributed to the increase of the competing non-radiative recombination due to shallow dislocation states. In opposition to the indirect luminescence, the character of the direct Ge luminescence, i.e. incline of intensity upon growing temperature, is not converted by dislocations. The measured behavior of the direct peak position of Ge, in the temperature range between 80 and 300 K, is in accordance with calculated dependence and reflects the direct bandgap energy. The observed red shifts in dislocated Ge structures are shown to be produced by tensile strain, bandgap narrowing and by the Sn-content of GeSn quantum wells, respectively. A direct influence of dislocations could not be observed. Satisfying understanding of the existing temperature behavior of the indirect Ge peak position is on embryonic stage