Impedance spectroscopy analysis of AlGaN/GaN HFET structures

For HFET application a series of samples with 30 nm AlxGa1-xN (x = 0.02-0.4 ) layers deposited at 1040 degreesC onto optimised 2 mum thick undoped GaN buffers were fabricated. The AlxGa1-xN/GaN heterostructures were grown on c -plane sapphire in an atmospheric pressure, single wafer, vertical flow MOV PE system. Electrical properties of the AlxGa1-xN/GaN heterostructures and thick undoped GaN layers were evaluated by impedance spectroscopy method pe rformed in the range of 80 Hz-10 MHz with an HP 4192A impedance meter using a mercury probe. The carrier concentration distribution through the layer thickness and the sheet carrier concentration were evaluated. A nondestruct ive, characterisation technique for verification of device heterostucture q uality from the measured C - V and G - V versus frequency characteristics o f the heterostructure is proposed. (C) 2001 Elsevier Science B.V. All right s reserved.