Electron Transport Properties in High Electron Mobility Transistor Structures Improved by V-Pit Formation on the AlGaN/GaN Interface
A. Hospodková, František Hájek, Tomáš Hubáček, Zuzana Gedeonová, Pavel Hubı́k, Matěj Hývl, J. Pangrác, Filip Dominec, Tereza Košutová
Abstract
High Resolution Image Download MS PowerPoint Slide This work suggests new morphology for the AlGaN/GaN interface which enhances electron mobility in two-dimensional electron gas (2DEG) of high-electron mobility transistor (HEMT) structures. The widely used technology for the preparation of GaN channels in AlGaN/GaN HEMT transistors is growth at a high temperature of around 1000 °C in an H 2 atmosphere. The main reason for these conditions is the aim to prepare an atomically flat epitaxial surface for the AlGaN/GaN interface and to achieve a layer with the lowest possible carbon concentration. In this work, we show that a smooth AlGaN/GaN interface is not necessary for high electron mobility in 2DEG. Surprisingly, when the high-temperature GaN channel layer is replaced by the layer grown at a temperature of 870 °C in an N 2 atmosphere using TEGa as a precursor, the electron Hall mobility increases significantly. This unexpected behavior can be explained by a spatial separation of electrons by V-pits from the regions surrounding dislocation which contain increased concentration of point defects and impurities.