Room temperature low frequency noise characteristics of gate and drain currents of an AlGaN/GaN high electron mobility transistor are reported. A Hooge parameter (αH) ranging from 10−3 to 10−4 is extracted for drain current noise as a function of sheet carrier density. Gate current noise is simultaneously measured with drain noise both in the time and frequency domain. A weak correlation is seen between the drain and gate noise. Temporally unstable Lorentzian components on top of stable 1/fγ noise are observed in the gate noise spectra which also show up as random telegraph signal noise in the time domain. It is proposed that the gate Schottky contact is of high quality but that electrically unstable point defects in the AlGaN layer are the cause of Lorentzians and random telegraph switching noise.

Low frequency noise characteristics of gate and drain currents are investigated for prestressed and poststressed AlGaN/GaN high electron mobility transistors. High reverse bias voltage stresses on the gate stack changes both drain and gate current noise. A temporary increase in drain current noise was observed during stress which recovered to prestress level a few weeks later. This is explained via a positive and negative threshold voltage shift due to electron trapping under the gate during and after stress, respectively. On the other hand, gate current noise shows a permanent increase after the stress which is not seen to recover once the stress is removed. It is proposed that new defect states are created below the metal AlGaN layer of the gate edges which leads to a permanent degradation of gate current noise.

The authors fabricate vertical geometry single-walled carbon nanotube (CNT) film/p-type silicon Schottky barrier photodetectors, where the CNT film acts as the transparent metal and silicon as the active semiconductor. The authors experimentally characterize the current-voltage, spectral responsivity, and noise properties of these devices under reverse bias. The authors find that the CNT film–Si Schottky barrier photodetectors exhibit a large photocurrent-to-dark current ratio with responsivity as high as 0.10 A/W due to the high transmittance of the CNT film. The measured current noise spectral density shows a 1/f limited behavior and scales as the square of the reverse bias current. The noise equivalent power of the devices is found to be 1.4 × 10−10 W. A comparison between CNT film devices and devices based on conventional metal electrodes is also carried out. These results provide important insights into the properties and performance of CNT film–Si Schottky barrier photodetectors.

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Room temperature gate leakage current measurements as a function of gate bias voltage are reported for different AlGaN/GaN high electron mobility transistors and interpreted in terms of space charge limited flow in the presence of shallow traps through very small area conductive leakage paths already present or formed under electrical stress in the gate stack device area. Transport parameters for electrons following these paths are extracted, and the observation of gate electron velocity saturation in stressed devices indicates that newly created leakage paths form predominantly in high electric field gate edge regions.