Enhanced Electron Mobility GaN Transistor (EEMT)

Our technical approach is based on a uniquely large (close to 3 eV for GaN) energy band shift in III-Nitride based p-n junctions. We propose to enhance electron mobility in the n-doped MESFET channel by localizing electrons at the surface using a lightlyp-doped GaN buffer layer (patent pending). This Enhanced Electron Mobility Transistor (EEMT) approach has several advantages. First, we have a good localization of carriers in the channel without using highly strained AlGaN/GaN heterointerfaces. Thislocalization introduced by the built-in electric field diminishes short-channel effects, improves transistor linearity, and decreases noise. Second, a large concentration of carriers at the channel interface should lead to filling interface statesresulting in better device performance. Third, this localization prevents the 2D-3D transition and should allow us to obtain a higher sheet carrier concentration. Our EEMT device design reduces the source and drain contact resistance, because ohmiccontacts will be fabricated on a high quality, highly doped GaN. EEMT design eliminates large built-in strain and, thus, is expected to yield a much better device stability, higher parameter uniformity across large diameter substrates, better manufacturingreproducibility, and substantially lower cost.We expect that the electron mobility enhancement due to a large built-in electric field will be sufficient to compete with conventional AlGaN/GaN HFETs, especially for short channel device designs.We therefore feel that the large periphery EEMT devices of the type whose feasibility we establish in Phase I, can become the key component for the MMIC modules. These modules will be useful for the T/R modules for the next generation high power mobileradars. Our technology will also have numerous commercial applications in high power and linear amplifiers for wireless communications