High electron mobility transistors with minimized performance effects of microcracks in the channel layers

摘要

In HEMTs based on III-nitrides epitaxial films or GaAs, AlGaAs and InGaAs epitaxial films, unwanted microcracks are often formed in the composite epitaxial layers in the channel region during fabrication and operation. These microcracks are caused by strain or stresses due to lattice mismatch and thermal expansion coefficient differences between materials and substrate's. Those microcracks will bring about an increase in source to drain resistance and lead to performance and reliability degradation of the HEMTs and the MMICs containing them. The present invention provides HEMTs with minimized effects of the unwanted microcracks by aligning the channel region long axis to a certain direction so that the channel region long axis forms a right angle with axis of at least one type of the microcracks.