Patent ID: 11049718

Abstract:
The invention relates to a method to reduce the contact resistance of ohmic contact in group III-nitride high-electron mobility transistor (HEMT). A heavily n-type doped nitride layer with modulation doping is epitaxially grown on selected contact regions for use as ohmic contact layer. The method for producing the n++ ohmic contact layer includes at least the following: deposition of nitride HEMT epitaxial structure on substrates (such as SiC, silicon, sapphire, GaN etc), deposition in-situ or ex-situ mask for selective growth of n-contact, selective etching to create of openings within the mask layer, deposition of modulation doped n++ nitride ohmic contact layer followed by ohmic metal deposition. The modulation doping involves alternating epitaxy of high and low doped nitride layers with common n-type dopant such as Ge, Si etc. The modulation doping significantly increases the range of n-type doping without detrimental effect on the material quality of the contact layer.