AlGaN/GaN Heterostructures: Fabrication and Electrical Characterization

Group III-nitrides, in particular GaN and its heterostructures with AlGaN, have some unique electronic material properties that make these material systems almost ideally suited for the fabrication of a number of high-performance electronic and optoelectronic devices. A study of MBE grown Al0.2Ga0.8N/GaN heterostructures was conducted. Rectifying and ohmic contacts were fabricated for electrical characterization of the heterostructure. These contacts were fabricated by sputter deposition of metal films. A multi-layer Ti/Al/Ni/Au (15/60/35/50nm) metallization and subsequent anneal was employed to form ohmic contacts. A contact resistivity of 2.0 x 10-3 Ohm.cm2 was obtained. Though this value was high but was expected of unintentionally doped n/n Ni Al0.2Ga0.8N/GaN unipolar heterostructure. Rectifying contacts were obtained by depositing Ni on the AlGaN/GaN film, overcoated with Au (Ni/Au, 20/180nm). Fabricated HEMT devices exhibited transistor behavior with transconductance values between of 1.0 and 2.5 mS; however, saturation was not observed. A drift mobility ~130 cm2/V.s was estimated from the calculated transconductance.

Autorentext

Michael A. Awaah received his MSc. in Electrical Eng. from Belorussian State Polytechnic Academy in 1993, MS in in Electrical Eng., 2002 and PhD in Material Science and Eng., 2006 from Tuskegee University, AL. He currently service as Assistant Professor of Electrical Eng. at Tuskegee University. He previously worked with Intel Corp.