We examine the temperature dependence of the piezoresistive coefficients of silicon carbide (SiC) and gallium nitride (GaN) crystals, which are prospective materials for hightemperature applications owing to their wide-bandgap properties. The temperature-dependent piezoresistive coefficients of these materials were obtained by modeling experimental resistance changes using thermomechanical numerical simulations. This work reports the piezoresistive coefficients of 4H-SiC and GaN at the high-temperature environments, which are still not well researched. The results revealed that the temperature dependences of piezoresistive coefficients were strongly related to the ionization energy, and a high ionization energy stabilized the values of the piezoresistive coefficients at high temperatures. Our proposed temperature modeling method helps in predicting the temperature dependence of the piezoresistive coefficient using the value at the room temperature and the ionization energy of the material, which is useful for evaluating the piezoresistive effect at different temperatures during device simulations.

β-Ga2O3 has a high potential for power device applications because of a high Baliga’s figure and the availability of large-scale wafers. However, the piezoresistive effect of β-Ga2O3 has not been investigated in detail, and its piezoresistive coefficient has not been reported. This study evaluates the piezoresistive coefficient of β-Ga2O3 in the <010> direction using a mechanical stress simulator and a device simulator, which includes our piezoresistive effect model. In this study, the piezoresistive effect model and simulation method are applied to β-Ga2O3 for the first time. The piezoresistor model of β-Ga2O3 is simulated to evaluate the piezoresistive coefficient of β-Ga2O3. The experimentally obtained gauge factor with and without the contact effect is −5.8 and −3.6, respectively. The piezoresistive coefficient with and without the contact effect is −2.0 × 10−11 Pa−1 and −1.2 × 10−11 Pa−1, respectively. The piezoresistive coefficient is used to evaluate the piezoresistive effect at 1000 °C through thermal analysis.

This study examined the temperature-related piezoresistance issues of p-type doped 3C-silicon carbide (3C-SiC) materials. Previously, we proposed piezoresistance temperature models that describe phenomena based on the ionization energies of materials oriented for high-temperature operations. This study aimed to determine the ionization energy as a function of the aluminum doping concentration of 3C-SiC. However, at the low-temperature region a drastic decrease in the piezoresistive coefficient was observed, and it was predicted to occur when materials possessing large impurity ionization energy are used under negative thermal strained conditions. This phenomenon is in contrast to the conventional piezoresistance factor P (N, T ) that is based on narrow band-gap materials such as silicon or germanium; thus, it provides new insights into low-temperature piezoresistance phenomena.