Zero-Bias Mixer Based on AlGaN/GaN Lateral Field-Effect Diodes for High-Temperature Wireless Sensor and RFID Applications

In this paper, a zero-bias mixer using a lateral field-effect diode fabricated on standard GaN-on-Si AlGaN/GaN high-electron-mobility-transistor wafers is demonstrated. The diode features strong nonlinearity near zero bias, enabled by a threshold-voltage modulation using a fluorine-plasma-treatment technique. The maximum change in conductance was adjusted to ~0 V, leading to optimal conversion loss (CL) of the mixer at zero bias and eliminating the need for any dc supplies. The mixer is characterized from room temperature (RT) to 250degC . At 2.5 GHz and at RT, the CL and third-order intermodulation intercept point are 12.9 dB and 17.64 dBm, respectively. The operation of the proposed diode is modeled by a physical equivalent circuit, with the element values extracted from the measured S-parameters. The voltage-biasing dependence of the CL can be explained by the model. The high-temperature operation of the mixer shows that the proposed mixer can perform well in high-temperature and ultralow-power applications.