Experimental Studies of Al_(0.12)Ga_(0.88)N/GaN Heterostructure Varactors in View of Frequency Increases

摘要

We report on a study regarding the performance of double-barrier heterostructure varactors based on Al_(0.12)Ga_(0.88)N/GaN when compared with Al_(0.70)Ga_(0.30)As/GaAs ones. The limitations are coming from the required decrease of the content of the aluminium in the barrier, which reduces the polarization charge effect and leads to a low barrier and a low figure of merit which limits the cut-off frequency of the device. As was previously shown, the polarization charge which form at the interfaces of the nitride materials with high values of x, create a non-symmetry in the D.C. and small signal characteristics, making corresponding Al_xGa_(1-x)N/GaN HBV unsuitable for high frequency applications. However, the higher electric field that can be sustained by the GaN material is a great advantage over GaAs and InGaAs because we can apply higher RF bias, thus allowing us to get more harmonic power. By stalking more than two barriers together, the overall performance of the device was expected to be improved, by means of output power and cut-off frequency.