Polarization-induced electrical conductivity in ultra-wide band gap AlGaN alloys

Unintentionallydoped (UID)AlGaN epilayers graded overAl compositions of 80% –90% and 80%–100% weregrown by metal organic vapor phase epitaxy and were electrically characterized using contactless sheetresistance (Rsh) and capacitance-voltage (C –V) measurements. Strong electrical conductivity in the UID gradedAlGaN epilayers resulted from polarization-induceddoping and was verified by the lowresistivity of 0.04 Ω cm for theAlGaN epilayer graded over 80% –100%Al mole fraction. A free electron concentration (n) of 4.8  × 1017  cm−3 was measured byC –V forAl compositions of 80% –100%. Average electron mobility (μ¯) was calculated fromRsh andn data for three ranges ofAl composition grading, and it was found that UIDAlGaN graded from 88% –96% hadμ¯ = 509 cm2/V s. The combination of very largeband gapenergy, highμ¯, and highn for UID gradedAlGaN epilayers make them attractive as a building block for high voltage power electronic devices such asSchottky diodes andfield effect transistors.

Source: Applied Physics Letters - November 28, 2016 Category: Physics Authors: Andrew M. Armstrong and Andrew A. Allerman Source Type: research