Low-k BCB passivated Al_0.5Ga_0.5As/In_0.15Ga_0.85As enhancement-mode pHMETs

A high power-added efficiency Al_0.5Ga_0.5As/InGaAs enhancement-mode pHEMTs with benzocyclobutene (BCB) passivated layer are fabricated and characterized. This passivation technology takes advantages of the low dielectric permittivity (2.7) and a low loss tangent (0.0008), which simplifies the passivation process for microwave power device. In this work, we not only suppress the drain-source breakdown voltage but also improve the device power performance under a high input power swing by using a BCB passivation layer. The passivated 1.0 μm-long gate pHEMTs exhibit a higher off-state performance than unpassivated ones. The maximum output power under a 2.4 GHz operation is 118 mW/mm, with a linear power gain of 11.1 dB, and a power-added efficiency of 60 %. These characteristics demonstrate a great potential for BCB passivated E-mode pHEMTs on the large-signal microwave power device applications.