Low-frequency noise in AlGaN/GaN heterojunction field effect transistors on SiC and sapphire substratesThe low-frequency noise is studied in different AlGaAs/ GaAs heterostructures under electric biases as a function of the temperature. The heterostructures differ in the two-dimensional electron-gas density and the mobility. In addition to the thermal noise, different contributions are found and characterized ͑1/ f and generation-recombination noises͒. The presence of the generation-recombination noise is linked to defects in the interface between the channel and electrical contacts. Thermal activation energy values are deduced from Arrhenius plots and related to As Ga antisite defects and DX centers. The 1 / f noise is also characterized and its origin is identified as being the carrier mobility fluctuation dominated by lattice phonons.

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Bidirectional electric stresses are performed in metal—oxide—silicon capacitors with ultrathin (2.5 nm) oxides and with highly doped substrates. The observed effects are compared to those occurring under the conventional unidirectional constant-current overload. The effects observed after stress of ultrathin oxides bring into play defects of comparable nature to those noted for thick oxides, namely, neutral traps. Furthermore, soft breakdown events are scrutinized based on defect creation throughout the oxide and modulation of charge state trapping at the interfaces.