Fiodor F. Sizov

Sub-THz radiation room temperature sensitivity of long-channel silicon field effect transistors

Room temperature operating n-MOSFETs (n-type metal-oxide silicon field effect transistors) used for registration of sub-THz (sub-terahertz) radiation in the frequency range ν = 53−145 GHz are considered. n-MOSFETs were manufactured by 1-μm Si CMOS technology applied to epitaxial Si-layers (d ≈15 μm) deposited on thick Si substrates (d = 640 μm). It was shown that for transistors with the channel width to length ratio W/L = 20/3 μm without any special antennas used for radiation input, the noise equivalent power (NEP) for radiation frequency ν ≈76 GHz can reach NEP ∼6×10−10 W/Hz1/2. With estimated frequency dependent antenna effective area Sest for contact wires considered as antennas, the estimated possible noise equivalent power NEPpos for n-MOSFET structures themselves can be from ∼15 to ∼103 times better in the specral range of ν ∼55–78 GHz reaching NEPpos ≈10−12 W/Hz1/2.

Charge transport in HgCdTe-based n+-p photodiodes

It is shown that dark currents measured at 77 K in Hg1−xCdxTe (x⋍0.21) homojunctions can be adequately described by the balance equations with allowance made for the two main charge-transport mechanisms, i.e., tunneling assisted by traps in the band gap and recombination via these traps; the above homojunction may find application in microphotoelectronics in the infrared spectral range of 8–12 µm. Other charge-transport mechanisms are included in the consideration as additive terms. A comparison between the experimental current-voltage characteristics and dynamic resistance of HgCdTe diodes with the results of calculations was carried out. A good agreement was obtained between experimental data and the results of calculations, in which the donor and acceptor concentrations in the n and p regions of diodes, the concentration of traps and the position of their levels in the band gap, and the lifetimes of charge carriers for recombination via these traps were used as adjustable parameters.

The nature of emission of porous silicon produced by chemical etching

The structural and luminescence characteristics of porous silicon produced by chemical etching are studied. From analysis of the behavior of luminescence spectra with temperature, it is shown that the luminescence band of porous silicon samples produced by chemical etching presents a superposition of two bands. It is concluded that one of the bands is due to excitonic recombination in amorphous silicon nano-clusters smaller than 3 nm in dimensions and the other band corresponds to recombination of charge carriers via defects in silicon oxide. At room temperature, the latter band prevails.

Properties of 2x64 linear HgCdTe MBE-grown LWIR arrays with CCD silicon readouts

Mercury-Cadmium-Telluride (MCT) 2 X 64 linear arrays with silicon readouts were designed, manufactured and tested. NCT layers were grown by MBE method on (103) GaAs substrates with CdZnTe buffer layers. 50 X 50 mm n-p-type photodiodes were formed by 80 divided by 120 keV boron implantation. The dark current at 100 mV reversed biased diodes was within 15*30 nA and zero bias resistance-area product was within R0 approximately equals 20 divided by 50 Ohm X cm2. Silicon read-out circuits were designed, manufactured and tested. Read-outs with skimming and partitioning functions were manufactured by n-channel MOS technology with buried or surface channel CCD register. The parameters of LWIR MCT linear arrays with cutoff wavelength (lambda) co 10.0 divided by 12.2 micrometers and Si readouts were tested separately before hybridization. The HgCdTe arrays and Si readouts were hybridized by cold welding In bumps technology. With skimming mode used for integration time of 24-30 ms for such MCT n-p-junctions, the detectivity D*(lambda ) approximately equals 4 X 1010 cmXHz1/2/W. Dark carrier transport mechanisms in these diodes were calculated and compared with experimental data. Two major current mechanisms were included into the current balance equations: trap-assisted tunneling and Shockley-Reed-Hall generation-recombination processes via a defect trap level in the gap. Other current mechanisms (band-to-band tunneling, bulk diffusion) were taken into account as additive contributions. Tunneling rate characteristics were calculated within k-p approximation with the constant barrier electric field. Relatively good agreement with experimental data for diodes with large zero resistance-area products (R0A > 10 OhmXcm2) was obtained.

Readout device processing electronics for IR linear and focal plane arrays

Silicon read-out devices with input direct injection and buffered direct injection circuits and charge coupled devices (CCD) multiplexers to be used with n+-p- or p+-n-photovoltaic (PV) multielement arrays were designed, manufactured and tested in T equals 77-300 K temperature temperature region. Into these read-out devices were incorporated the testing switches which attach the sources of direct injection transistors to the common load resistors to imitate the output signal of mercury cadmium telluride photodiodes. The silicon read-out devices for 2 X 64 n+-p- or p(superscript +n- linear arrays and n(superscript +-p-2 X 4 X 128 time delay and integration arrays with skimming and partitioning functions were manufactured by n- or p-channel MOS technology with buried channel CCD register. The designed CCD readout devices are driven with four- or two-phase clock pulses.

Testing of readout device processing electronics for IR linear and focal plane arrays

For preliminary selection of the silicon read-out devices designed for applications in hybrid mercury-cadmium-telluride (MCT) IR linear or matrix arrays manufactured according to flip-chip technology, there was designed constructions of the testing circuits imbedded into the read-out devices to test them before hybridization. Also the procedure of their testing at room temperature without attachment to the MCT photo- voltaic multielement arrays was developed. There were designed some types of multielement silicon read-out devices with input direct injection and buffered direct injection circuits and charge coupled devices (CCD) multiplexers to be used with n+-p- or p+-n-photodiodes with dynamical resistance at reverse bias R greater than or equal to 107 (Omega) . Into these read-out devices there were incorporated the testing switches which attach the sources of direct injection transistors to the common load resistors to imitate the output signal of MCT photodiodes. The silicon read-out devices for 2 X 64 linear arrays and 2 X 4 X 128 (144) TDI arrays with direct and buffered direct charge injection were manufactured by n-channel MOS technology with CCD register with buried channel. By changing the frequency of the control impulses here were investigated the characteristics of the read-out devices for time delay and integration (TDI) arrays in the regime of integration and without it (in TDI channel).

Mechanisms of dark conductivity and photosensitivity in PbSe polycrystalline films on glass and Si substrates

Temperature dependencies of dark electrical characteristics (Hall effect and conductivity) are investigated in PbSe polycrystalline films with different crystallite sizes deposited on glass and Si substrates. In these films the spectral dependencies of photoelectrical characteristics and the lifetime of photoexcited carriers on the crystallite sizes are studied. It is shown that the experimental data may be explained by the existence of the potential barriers for the majority carriers (holes ) at the grain boundaries. The height of the barriers is found to depend on the crystallite sizes. PbSe photosensitive structures with detectivity D[sup [star]][sub [lambda]] = 2 [times] 10[sup 10] cm Hz[sup [1/2]]/W at room temperature are fabricated on glass substrates. On Si substrates, the detectivity values of PbSe polycrystalline photodetectors were an order lower.

Superconducting states of lead nanoinclusions in the stoichiometric PbTe matrix

Phase states of lead nanoinclusions in stoichiometric lead telluride in magnetic fields from 0 to 1 kOe are studied in the region of temperatures below the temperature of transition of lead to superconducting state (T = 1.7−6.5 K). It is shown that the lead nanoinclusions behave like type-I superconductors. The sizes of lead nanoinclusions that are in the superconducting state at 1.7 K are no smaller than 200 nm. The experimental temperature dependence of the diamagnetic additional component can be interpreted in the context of a model that takes into account the existence of an “intermediate” superconducting state caused by the geometric parameters of lead nanoinclusions.

Silicon field-effect transistors as radiation detectors for the Sub-THz range

AbstractThe nonresonance response of silicon metal-oxide-semiconductor field-effect transistors (Si-MOSFETs) with a long channel (1–20 μm) to radiation in the frequency range 43–135 GHz is studied. The transistors are fabricated by the standard CMOS technology with 1-μm design rules. The volt-watt sensitivity and the noise equivalent power (NEP) for such detectors are estimated with the calculated effective area of the detecting element taken into account. It is shown that such transistors can operate at room temperature as broadband direct detectors of sub-THz radiation. In the 4–5 mm range of wavelengths, the volt-watt sensitivity can be as high as tens of kV/W and the NEP can amount to