In this paper, electro-thermo-mechanical coupled static and dynamic FEM simulations are adopted to study the AlGaN/GaN pressure sensor. The sensor sensitivity is expressed as the drain current change of transistor integrated on the AlGaN/GaN cantilever or circular diaphragm with the applied pressure, namely piezoresistive effect, which is caused essentially by the change of piezoelectric polarization charge. In the static simulation study, how the transistor selfheating, gate metal layer, AlGaN donor-like surface states, and bulk acceptor-like traps in GaN influence the sensitivity are separately illustrated. In the dynamic simulation study, transient behavior of the sensor with the bulk acceptor-like traps and dependences of the natural frequency of circular diaphragm on the self-heating as well as the position of transistor integrated on the diaphragm are analyzed. This work would provide useful guidelines for the design and optimization of AlGaN/GaN pressure sensor.

The gate leakage current (I G ) of AlGaN/GaN high electron mobility transistors (HEMTs) at various ambient temperatures is simulated by considering its mechanism as domination of trap-assisted tunneling (TAT) and Poole-Frenkel (PF) emission for low electric field in the AlGaN barrier, and domination of Fowler-Nordheim (FN) tunneling for high electric field in the AlGaN barrier. Two bias cases are studied: V GS (gate voltage) variation while V DS (drain voltage) = 0 V without self-heating and V DS variation while V GS = 0 V with self-heating. For the first case, FN tunneling current mainly concentrates near the gate edges and so it is not changed with the gate length. While PF emission and TAT current do not show big variation along the gate, they are affected by the gate length and show higher values for longer gate. For the second case, with V DS increasing the elevated device temperature caused by the self-heating obviously increases PF emission and also increases I G because PF emission is the dominant mechanism of I G . With V DS further increasing, although the higher device temperature presents, I G is not affected by the self-heating because the temperature-independent FN tunneling becomes the dominant mechanism of I G . AlGaN/GaN high electron mobility transistors (HEMTs) present a big potential used in the field of high power, high temperature, and high frequency due to the wide bandgap of the materials as well as high electron mobility and saturation velocity in the transistors, which have attracted lot of researches in the past. Modelling/simulation and illustration of relevant mechanism of the gate leakage current (I G ) are important research aspects for AlGaN/GaN HEMTs, because usually I G can affect the device power efficiency and reliability. So far, some possible mechanisms of I G have been proposed: based on the fact of high density of traps locating in the AlGaN barrier or on the AlGaN surface, I G could be formed by Poole-Frenkel (PF) emission 1 and phonon-assisted tunnelling; 2 due to the high electric field in the Schottky barrier, I G could be formed by Fowler-Nordheim (FN) tunneling 3 and thermionic field emission. 4,5The electric field and also the leakage current near the gate edges have higher values than that in the other regions of the gate, 6 especially for the device under relative low V GS . Generally, the leakage current near the gate edges is considered to be negligible and so it is omitted in I G modelling for AlGaN/GaN HEMTs with long gate. While for the device with short gate, the leakage current near the gate edges is obvious and therefore it would be considered in the modelling. As far as we know, in the past, I G modelling has not addressed the self-heating effect since the studies were restricted to the device with V DS keeping zero (no self-heating). For the device with high power consumption, the self-heating could significantly increase the device temperature, 7,8 and any temperature-dependent I G should be influenced by the selfheating. In this paper, we will address ...

In this paper, we develop three-dimensional fully coupled electro-thermal (ET) simulation for AlGaN/GaN high electron mobility transistors (HEMTs), which is a relative complete and accurate simulation compared to the current existed simulations, capable of describing the lateral ET behavior of the device. As applications of this simulation, we investigate impact of the gate width (WG) and number of the gate fingers (NG) on the steady and transient ET behavior of the device. The steady results show that the lateral heat dissipation and thermal crosstalk between the gate fingers significantly affects the ET behavior for the device with narrow gate and multifinger, respectively. However, the transient results show that, within a time scale after the device switching on, the ET behavior is not influenced by WG and NG, i.e., the lateral heat dissipation and thermal crosstalk have no effects. This indicates that when the device operating in high frequency, increasing WG and NG to improve the power output is not restricted by the self-heating.

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Due to the piezoelectricity, the density of 2DEG (NS) formed in the AlGaN/GaN heterostructure can be altered when it is deformed externally, which may be exploited to develop pressure sensors and to enhance the performance of power devices by stress engineering based on the heterostructure. In this paper, a 3D electro-mechanical simulation is presented to study how the induced strains and NS for the AlGaN/GaN wafer under bending exerted uniaxial stress are influenced by the edges caused by processing: the fabrication of the mesa used for isolation, the ohmic contact metal, the gate metal, and the passivation. Results show that the influences are dependent on distance between the edges, depth of the edges, and direction of the exerted uniaxial stress.