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We fabricated amorphous selenium (a-Se) photodetectors with a lateral metal-insulator-semiconductor-insulator-metal (MISIM) device structure. Thermal aluminum oxide, plasma-enhanced chemical vapor deposited silicon nitride, and thermal atomic layer deposited (ALD) aluminum oxide and hafnium oxide (ALD-HfO2) were used as the electron and hole blocking layers of the MISIM photodetectors for dark current suppression. A reduction in the dark current by three orders of magnitude can be achieved at electric fields between 10 and 30 V/μm. The effective dark current suppression is primarily ascribed to electric field lowering in the dielectric layers as a result of charge trapping in deep levels. Photogenerated carriers in the a-Se layer can be transported across the blocking layers to the Al electrodes via Fowler-Nordheim tunneling because a high electric field develops in the ultrathin dielectric layers under illumination. Since the a-Se MISIM photodetectors have a very low dark current without significant degradation in the photoresponse, the signal contrast is greatly improved. The MISIM photodetector with the ALD-HfO2 blocking layer has an optimal signal contrast more than 500 times the contrast of the photodetector without a blocking layer at 15 V/μm.

This paper reports a self-induced ferroelectric 2-nm-thick Ge-doped HfO2 (Ge:HfO2) thin film. Ge thermal desorption, incorporation into HfO2, and further Ge:HfO2 crystallization were all performed through rapid thermal annealing simultaneously. The ferroelectric property of a 2-nm-thick Ge:HfO2/2-nm-thick Al2O3 dielectric stack was confirmed using the polarization-electric field measurement. X-ray photoelectron spectroscopy was used to confirm that Ge bonded to HfO2 as Hf-germanates. Piezoresponse force microscopy was used to demonstrate the piezoelectric property of Ge:HfO2/Al2O3. Furthermore, a dielectric stack of Ge:HfO2/Al2O3 was applied as a gate insulator in a Ge nanowire gate-all-around ferroelectric field-effect transistor (Ge NW Fe-GAAFET). The device exhibited a minimum steep-sub-threshold slope of 47 mV/dec, a high ION/IOFF ratio of >106, and low gate leakage current; moreover, it was free of a drain-induced barrier lowering effect. The proposed self-induced ferroelectric Ge:HfO2 Ge NW Fe-GAAFET is feasible for future ultra-low power integrated circuit applications.

Highly stable HoScO3 with different thicknesses as the Cu diffusion barrier on Si is prepared and characterized. The ultrathin (3 nm) HoScO3 barrier scheme is stable after 50 h annealing at 400°C , while its electrical resistivity shows no noticeable increase after annealing at 600°C for 1 h. Both the 5 and 10 nm thick barrier schemes are stable up to 700°C according to the resistivity result. Transmission electron microscopy and Auger electron spectroscopy reveal that the ultrathin amorphous barrier is uniformly present at the interface after annealing at high temperatures. The results indicate that the 3 nm thick HoScO3 is an effective diffusion barrier for copper metallization.

In this study, we fabricated a-Se based photosensors with an alternating multilayer structure of a-Se and AsxSe1−x by rotational thermal evaporation deposition. During the deposition of the amorphous AsxSe1−x layers, As diffuses into the underlying a-Se component layers, thereby improving the thermal stability of the multilayer photosensor and thus increasing the breakdown electric field. Although the As doping introduces carrier traps in the a-Se layers, the multilayer photosensors demonstrate an effective quantum efficiency comparable to the single-layered a-Se sensor under the blue light illumination but are with a lower dark current density by two orders of magnitude. In addition to the top AsxSe1−x layer being functioning as an electron blocking layer, carrier traps present in the multilayer structure may decrease the drift mobility of charge carriers and disturb electric field distribution in the photosensors, thereby suppressing the dark current.