The asymmetric nano-channel diode (ANCD) is the 2-dimensional electron gas (2DEG) semiconductor nanodevice that, unlike a conventional diode, relies on the device nanostructure and field-controlled transport in a ballistic nanometerwidth channel instead of barriers to develop its asymmetric, diode-like current-voltage (I-V) characteristics. We focus on ANCD optoelectronic properties, and demonstrate that the devices can act as very sensitive, single-photon-level, visiblelight photodetectors. Our test structures consist of 2-μm-long and ~230-nm-wide channels and were fabricated using electron-beam lithography on a GaAs/AlGaAs heterostructure with a 2DEG layer, followed by reactive ion etching. The I-V curves were collected by measuring the transport current under the voltage-source biasing condition, both in the dark and under light illumination. The experiments were conducted inside a cryostat, in a temperature range from 300 K to 78 K. As an optical excitation, we used a 800-nm-wavelength, generated by a commercial Ti:sapphire laser operated either at a quasi-continuous–wave mode or as a source of 100-fs-wide pulses. The impact of the light illumination was very clear, and at low temperatures we observed a significant photocurrent Iph ~ 0.25 μA at temperature 78 K for the incident optical power as low as 1 nW, with a limited dark-current background. The magnitude of the device optical responsivity increased linearly with the decrease of the optical power, reaching for 1-nW optical excitation the value as high as ~400 A/W at room temperature and >800 A/W at 78K. The physics of the photoresponse gain mechanism in the ANCD arises from a vast disparity between the sub-picosecond transit time of photo-excited electrons travelling in the 2DEG nanochannel and the up to microsecond lifetime of photo-excited holes pushed towards the device substrate.
The electrochemical etching of porous silicon offers many diverse opportunities for production of complex porous silicon structures located not only on the surface but also in a bulk of the silicon devices. A specific technological regime, the photo-electrochemical etching can affect bulk of the silicon device but at the same time saving its textured surface almost unchanged. Our group is the first who investigated the silicon solar cells with textured surface modified by means of photo-electrochemical etching. Etched devices demonstrated better photoelectrical characteristics if compare ones with unmodified solar cells. Our current work presents results on research of solar cells photoelectrochemically treated in HF: ethanol solution. Applied etching regime allowed us to modify the emitter’s volume at the same time affecting only minimally the surface of the solar cell itself. SEM micrographs show the elevations, ripples, bumps, cracks etc. on the surface of photo-electrochemically treated solar cells. The optical ellipsometer spectra, optical microscope measurements results, SEM micrographs of surface morphology as well as light reflectivity of the photoelectrochemically treated and untreated surfaces of the solar cells investigated and discussed in this work.
Pronounced random telegraph signals have been observed in voltages measured across current-biased thin-film
YBa2Cu3O7-δ superconducting bridges containing laser-processed channels for easy vortex motion. The appearance of two-level and three-level telegraph noise in bridges with single and double laser-written channels, respectively, is interpreted as experimental evidence for intermittent channeled vortex flow in current induced dissipative state in
We report the results of experimental study of IR radiation detection in a bulk of compensated germanium. Au or Ni with deep levels in the forbidden energy ap was used as compensating impurities. In spite of great difference in their activation energies the change of electrical resistance of the samples under CO2 laser illumination indicated the similar rise of carrier density in the valence band which can not be explained only by means of direct hole activation character of the electrical conductivity of compensated semiconductors. Evaluation of spatial quantity of in-homogenates in compensated semiconductors confirmed the importance of energetic bands bending due to the existence of ionized impurities complexes for IR detection.