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Author: search.filters.author.Anandan, DeepakSubject: search.filters.subject.GaN

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Now showing 1 - 3 of 3
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    Study of Charge Trapping Effects on AlGaN/GaN HEMTs Under UV Illumination With Pulsed I-V Measurement
    (2020-06-01)
    Nagarajan, Venkatesan
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    Chen, Kun-Ming
    ;
    Chen, Bo-Yuan
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    Huang, Guo-Wei
    ;
    Chuang, Chia-Wei
    The charge trapping effects on AlGaN/GaN HEMTs under UV illumination are investigated using the pulsed current-voltage (I-V) measurement method. The test samples are unpassivated Schottky-gate HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) with SiN gate dielectric. For HEMTs, the dominant charge trapping sources are the surface trap states, whereas, for MIS-HEMTs, they are trap states in the SiN gate dielectric and GaN buffer. When these devices are shined with the UV light, the drain current increases apparently in both samples owing to the generated photocurrent. By combining the UV illumination and pulsed I-V measurement, we find out the UV light has less effect on the surface charge trapping in the unpassivated HEMTs. Moreover, in MIS-HEMTs, we observe the charge trapping in the SiN gate dielectric becomes more serious under UV illumination, whereas the charge trapping in the GaN buffer is suppressed significantly. These findings are important for designing a GaN-based HEMT for photonic applications. In addition, the different responses of the surface-, buffer-, and gate-dielectric-related charge trapping to the UV light suggest that it would be easier to distinguish the trap types by introducing the UV illumination during the pulse measurement.
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    Low-Frequency Noise Characterization of AlGaN & x002F;GaN HEMTs and MIS-HEMTs Under UV Illumination
    (2020-01-01)
    Nagarajan, Venkatesan
    ;
    Chen, Kun-Ming
    ;
    Lin, Hsin-Yi
    ;
    Hu, Hsin-Hui
    ;
    Huang, Guo-Wei
    The low-frequency noise characteristics of AlGaN & x002F;GaN HEMTs and MIS-HEMTs are investigated in the dark condition and under UV illumination. The test devices with a 3-& x03BC;m-thick GaN buffer and a 25-nm-thick Al0.22Ga0.78N barrier layer were fabricated on the silicon wafer. For MIS-HEMTs, a 25-nm-thick SiN layer was deposited as a gate dielectric. The measured low-frequency noises show a 1 & x002F;f spectrum and can be described by the carrier number fluctuation model. Different noise responses to the UV light between HEMTs and MIS-HEMTs were observed. By comparing the noise data in dark and under UV illumination, the noise sources under the gate and in the ungated gate-drain access region have been identified. From these results, we can find a design guideline to improve the noise and reliability of GaN-based devices for optoelectronic applications.
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    A simple extraction method for parasitic series resistances in GaN HEMTs considering non-quasi-static effects
    (2019-05-01)
    Nagarajan, Venkatesan
    ;
    Chen, Kun-Ming
    ;
    Wang, Huan-Chung
    ;
    Singh, Sankalp Kumar
    ;
    Anandan, Deepak
    A simple technique for extracting the bias-dependent parasitic series resistances of the GaN-based high electron mobility transistor (HEMT) is demonstrated in this paper. With considering the non-quasi-static effect in devices, new analytical Z-parameter formulations are derived to determine parasitic resistances using the curve-fitting algorithm. More accuracy parasitic resistances can be obtained over a wide fitting frequency range compared to the conventional method which ignores the non-quasi-static effect. Here the intrinsic parameters are then calculated directly from intrinsic Y-parameters after de-embedding the parasitic elements in the small-signal equivalent circuit. An excellent agreement between the measured and simulated S-parameters from 100 MHz to 40 GHz is achieved, which validates the feasibility of our method for extracting the bias-dependent parasitic resistances.