The Origin and Influence of Compensatory Current in AlGaN/GaN Type High Electron Mobility Transistor Heterostructures with Two Conducting Channels on the Hall Measurements

Abstract

The second conducting channel is created in AlGaN/GaN type high electron mobility transistor (HEMT) heterostructures deposited by the metal organic vapor phase epitaxy (MOVPE) technique, in which the pressure changes during the growth of the buffer GaN layer to ensure its high resistivity. It is stated that a second, parasitic, conducting channel is induced as a result of nonintentional doping that occurs at the GaN–GaN interface. The Hall measurements, in the wide range of temperatures, from 77 to 420 K, are used to obtain sheet resistivity, sheet carrier concentration, and electron mobility of the heterostructures. The theoretical model of the multilayer transport in AlGaN/GaN type HEMT heterostructures, based on an equivalent circuit, allows for estimation of compensatory current. Based on the theoretical model, the correction map for the Hall measurement of the samples with two conducting channels is evaluated. The measured electron mobility μmeas obtained from Hall measurement is applied for the determination of the 2D electron gas (2DEG) mobility μ1 of the samples with two conducing channels using the equation μ1 = αμmeas. It is observed that the appropriate correction coefficient α depends on second channel parameters, i.e. the sheet resistance and mobility of the second conducting channel.