Gradually buffered, delta-doped AlGaN/GaN/AlGaN Heterostructure Field-Effect Transistors

New structure GaN-based field effect transistors (FETs) are proposed to solve the problem. A composition graded buffer, aiming at eliminating dislocations arising from hetero-epitaxy interface and suppressing channel electrons spillover under negative gate bias, a Si-delta-doped GaN layer just below the two-dimensional electron gas (2DEG) channel, used for polarization fields screening as well as carrier supplier, are the major innovations of the new structure. We propose to use a composition-graded AlGaN transition layer in-between the AlN buffer and the GaN layer. This carefully designed transition layer will be insulating and can gradually accommodate the lattice mismatch between AlN and GaN, eliminating/alleviating the dislocation generation. The piled-up polarization fields, which could deplete the 2DEG channel, will be taken care of by inserting a Si-delta-doping layer in the vicinity to the channel. Simulations will be done to guide experiments and find out the interactions among the composition grading, polarization fields and Si-delta-doping (concentration and position).