The invention relates to a transistor structure comprising an silicon carbide (SiC) substrate; a InGaN barrier layer is disposed on the substrate; a AlxGal.xN lower channel layer disposed on said barrier layer, where x is the concentration of Al content in said lower channel layer; and a A10.30GavoN upper channel layer disposed on said upper channel. The InGaN back-barrier for lower channel improves the carrier confinement in the channel of the HEMT device. These HEMT devices are operated with gain linearity up to a larger value for input power and frequency. The double channel back-barrier devices have good current gain and power gain cut-off frequencies and have a better gate control for the lower channel up to a higher drain to source voltages.