Influence of oxygen and methane plasma on the electrical properties of undoped AlGaN/GaN heterostructures for high power transistors

Plasma-induced damage often reduces the electrical and optical performance and the lifetime of compound semiconductor devices. We have investigated th e effect of oxygen and methane reactive ion etching plasma on the electrica l characteristics of nominally undoped GaN/Al0.25Ga0.75N/GaN high mobility heterostructures on sapphire substrates grown by plasma-induced molecular b eam epitaxy and metalorganic chemical vapor deposition (MOCVD). The electri cal transport properties of the two-dimensional electron gas in the AlGaN/G aN heterostructures were investigated by a combination of capacitance-volta ge profiling and Hall effect measurements. The performance degradation of t he heterostructures is attributed to the reduction of the carrier density a nd mobility due to ion bombardment, which is causing a creation of surface and deep acceptor states. After rapid thermal annealing (RTA) at temperatur es between 400 degrees C and 800 degrees C, the electrical properties of th e heterostructures exposed at moderated plasma power density and bias were mostly recovered. However, samples exposed at high power density lost the s ignificant part of the electron sheet carrier concentration unrecoverable e ven after RTA at 800 degrees C. (C) 2000 Elsevier Science Ltd. All rights r eserved.