Pulse behavior of insulated-gate double-field-plate power AlGaN/GaN HEMTs with C-doped buffers showing small current-collapse effects and dynamic RDS,on increase can accurately be reproduced by numerical device simulations that assume the CN-CGa autocompensation model as carbon doping mechanism. Current-collapse effects much larger than experimentally observed are instead predicted by simulations if C doping is accounted by dominant acceptor states. This suggests that buffer growth conditions favoring CN-CGa autocompensation can allow for the fabrication of power AlGaN/GaN HEMTs with reduced current-collapse effects. The drain-source capacitance of these devices is found to be a sensitive function of the C doping model, suggesting that its monitoring can be adopted as a fast technique to assess buffer compensation properties

The electrical transport properties of (BaCuO 2 ) 2 /(CaCuO 2 ) 2 superconducting artificial structures, grown by pulsed laser deposition stacking in sequence nonsuperconducting individual BaCuO 2 and CaCuO 2 layers, have been studied. Such artificially layered materials have T c values up to 80 K and show a number of unusual properties such as the relatively high normal state resistivity with a nonlinear dependence on temperature, the enhanced thermodynamic fluctuations, the relatively low value of the critical temperature with respect to the natural compounds with the same number of CuO 2 planes, and the same carrier concentration. It is demonstrated that such properties can be explained if the high level of structural disorder, typical of these artificial structures, is considered.

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Layer-by-layer pulsed-laser deposition has been used to grow ultrathin superconducting (Ba0.9Nd0.1)CuO2+x/CaCuO2 artificial structures with various thicknesses of the two constituent layers. Superconductivity was observed in the ultrathin structure consisting of a single CaCuO2 superconducting block sandwiched between two (Ba0.9Nd0.1)CuO2+x blocks. The results obtained allowed an experimental demonstration of the currently accepted structural model for high TC superconductivity, which requires the presence in the same structure of two blocks with different functional properties: the superconducting infinite layer block and the nonsuperconducting charge reservoir block.

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