AlGaN/GaN Heterostructure Field Effect Transistors

For high-power and high- frequency applications in electron devices, the growth of an AlGaN/GaN two-dimensional electron gas (2DEG) structure with a higher electron mobility and larger carrier density has been investigated. In the actual FET process, a high-temperature annealing is required to form Ti/Al ohmic contacts (~800 °~C), so the thermal stability of the thin AlGaN layer and 2DEG structure is very important. The seminar will discuss the effect of sheet resistance (Rs) increase upon annealing on FET performance and uniformity. The effect of dislocations on the current-voltage (I-V) characteristics of n-GaN Schottky contacts is also evaluated. The key feature of our measurements is the combination of sub-micrometer contact formation by electron beam (EB) lithography and precise I-V measurements by atomic force microscopy (AFM) with a conductive probe. Finally, the annealing temperature dependence of AlGaN/GaN HEMT sheet resistance combined with precise AlGaN thickness measurements will be discussed in conjunction with thermal stability considerations.