Search

Highlights • Two-dimensional electron gas was formed by growing AlGaN on GaN using MOCVD method. • The AlGaN/GaN van der Pauw device was fabricated and characterized. • Excellent linearity between output voltage and strain and excellent repeatability. Abstract This work reports the strain dependence of the offset voltage in an AlGaN/GaN van der Pauw device under mechanical strain. The AlGaN/GaN heterostructure was grown on a sapphire (0 0 0 1) wafer by using a metal organic chemical vapor deposition (MOCVD) process. Taking advantage of the four-terminal configuration, the fabricated van der Pauw device exhibited an excellent repeatability and linearity with a significant change of the offset voltage under application of tensile and compressive strains. In particular, the sensitivity of the device to the applied strain was found to be as large as 3 (μ V/V)/ppm, indicating the feasibility of using this effect for mechanical sensing applications. The sensing mechanism of the device is explained via the alteration of the sheet carrier concentration at the AlGaN/GaN interface and the asymmetric current flux in the 2DEG van der Pauw device. [ABSTRACT FROM AUTHOR]

Transistor-based on Gallium Nitride (GaN) technology, has enabled energy-saving power electronics to alleviate global energy utilization. Being the initial stages of the development as compared to mature Silicon (Si) technology, the critical issues related to the reliability of GaN-based devices are not much explored. To better understand the device reliability, the article reviews and summarizes, the trapping induced threshold voltage (V T H) instability and dynamic ON-resistance (R D S , O N) degradation specifically, for normally-off p-GaN gate HEMTs in power applications. The variation in threshold voltage and dynamic ON-resistance is examined for different operating regimes, which include biasing voltage and temperature. Furthermore, the characterization methods and test setups are discussed in detail to extract the true value of R D S , O N observed in the GaN power converter. Various models and techniques are reviewed as well which improves the converter conduction losses, introduced by dynamic ON-resistance. Additionally, different techniques are discussed in the review to control the V T H instability. It is observed that the point and extended defects created during device fabrication or charge trapping in GaN buffer, AlGaN layer, surface, or at their interface, induce variation in (V T H) and R D S , O N , for both the gate and drain stress regimes. Threshold voltage stability is mainly affected by the traps below the gate region, while the traps across the gate to drain access region influence the R D S , O N. The variation in R D S , O N value, is seen to be dependent on stress time, different device technology, and, switching conditions (frequency and duty cycle). In power application, the dynamic resistance shows a more pronounced effect on converter efficiency as compared to the V T H. • The article addresses the reliability issues in p-GaN Power HEMTs. • Mainly the trapping-induced V TH instability and R DS, ON degradation are considered. • Various characterization method and test-setup are discussed to extract R DS, ON value. • Methods to control R DS, ON degradation and V TH instability are studied. [ABSTRACT FROM AUTHOR]

The mobility of current carriers in the channel of FETs usually depends on the applied gate voltage. This paper presents experimental evidence that the electron mobility in the 2-D electron gas under the gate of AlGaN/GaN high-electron-mobility transistors (HEMTs) is actually independent of the gate voltage. This demonstration of the gate-voltage independence of the electron mobility relates to power HEMTs, and it was achieved by introducing a new method for the mobility measurement. The gate-voltage independence of the electron mobility was observed for a wide range of temperature, from 25 °C to 300 °C. Furthermore, it is confirmed that the HEMT mobility decreases with increased temperature according to the power law ( T^-k ) and with a quite high value of the power-law coefficient ( $k = 2.45$ ). [ABSTRACT FROM PUBLISHER]

In this paper, a novel method for extraction of electron mobility in the two-dimensional electron gas (2DEG) under the gate of power HEMTs is presented. Using this method enables the potential impact of the gate metal and the gate voltage on electron mobility in the 2DEG under the gate to be measured without the error due to the resistive regions outside the gate, which are the gate-to-source and gate-to-drain regions. The application of the new method was demonstrated by measurements on fabricated circular HEMTs. [ABSTRACT FROM AUTHOR]