Abstract: The present invention is related to high electron mobility transistors for power switching and microwave amplification and switching. More specifically, it related to a high electron mobility transistor with an improved gate to enhance the performance. When fabricating a high electron mobility thin film transistors, a first gate metal layer made of chromium alloy or tungsten alloy is deposited to reduce surface traps and to enhance the stability and integrity of the gates.

Abstract: Photonic Band Gap (PBG) structures are utilized in microwave components as filters to suppress unwanted signals because they have the ability to produce a bandstop effect at certain frequency range depending on the structural dimensions. The unique property of PBG structures is due to the periodic change of the dielectric permittivity so interferences are created with the traveling electromagnetic waves. Such periodic arrangement could exist either inside of the dielectric substrate or in the ground plane of a microstrip transmission line structure. This invention provides tunable or switchable planar PBG structures, which contains lattice pattern of periodic perforations inside of the ground plane. The tuning or switching of the bandstop characteristics is achieved by depositing a conducting island surrounded by a layer of controllable thin film with variable conductivities.