Investigation of breakdown behavior for AlGaN HEMTs

摘要

The ability to accurately determine the breakdown voltage of microwave transistors is critical to the design of high power microwave amplifiers. The optimal bias point and output impedance should be selected to ensure that the load line of the device during peak output power does not intersect the portion of the IV curve where the device breaks down [1]. A technique that has proven useful for the measuring off-state breakdown voltage for FETs was reported on by Bahl and del Alamo in 1993 [2]. This procedure works well for a variety of devices including microwave GaAs MESFETs, as described in the original article, and GaAs HEMTs. Fig. 1 shows the circuit diagram for the gate breakdown measurement system. The procedure for the measurement consists of using a current source to force a fixed current through the drain. The voltage on the gate is swept from zero to a negative value, while the voltage on the drain is allowed to float to whatever value is required to force the drain current. Bahl and del Alamo use a rule of thumb for the drain current of 1mA/mm [2]. This has proven to be a useful standard for GaAs MESFETs and HEMTs.