RF performance of high temperature diamond MESFET

DC and RF performance of p-type diamond MESFETs (Metal-Semiconductor Field Effect Transistors), is critically evaluated, especially for high temperature application. The investigation utilizes a theoretical large-signal RF model using a harmonic balance technique and the results are compared to experimental measurements. It is shown that the DC and RF performance of diamond MESFET is improved with temperature in an operating temperature range of 300 K to 923 K. The improvement of device performance with temperature can be attributed to a high value of activation energy (0.35 eV) for the ionization of boron. At 773 K, where essentially full activation occurs, the maximum RF output power at an operating frequency of 5 GHz is about 0.63 W/mm, and the maximum power-added efficiency (PAE) is 36% with the linear power gain of 9.4 dB. It is shown that the microwave power application of MESFETs in p-type diamond but otherwise conventional design is limited to high temperature.