Owing to their large band gaps and high dielectric constants, III-V nitrides are very attractive for high temperature electronics and optoelectronic device applications. Improved material properties have recently led to a variety of devices being demonstrated such as blue, green, and yellow light-emitting devices as well as laser diodes, metal-semiconductor GaN based fieldeffect transistors (MESFETs), and AlGaN/GaN based high electron mobility transistors (HEMTs). The presence of parasitic resistance can significantly limit performance such as lower speed for electronic devices and higher turn-on voltage for the optical devices. There is room for improvements for both n- and p- type ohmic contacts in order to lower parasitic resistance and improve reliability. W based contacts on GaN and InGaN have been demonstrated and show excellent thermal stability, however the contact resistivity still in the range of 10−5 Ω-cm2. By using InN and graded InGaN as the contact layers, the contact resistivity can be reduced to ∼ 10−6 Ω -cm2.
Besides low resistance ohmic contacts, a low leakage current and high turn-on voltage gate contact is critical to high performance electronic devices. Nitride based materials are very inert to conventional wet chemical etching used for other III-V compound semiconductors. Currently, dry etching is widely used for the device fabrication, however, III-nitrides are sensitive to dry etching, especially in the step of the gate recess etching. In this talk, metal insulator semiconductor (MIS) gate contacts based on AIN and Ga2O3/Gd2O3 will be discussed.