Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Near-surface processing on AlGaN/GaN heterostructures: a nanoscale electrical and structural characterization | Greco et al. Nanoscale Research Letters 2011 6 132 http content 6 1 132 o Nanoscale Research Letters a SpringerOpen Journal NANO REVIEW Open Access Near-surface processing on AlGaN GaN heterostructures a nanoscale electrical and structural characterization Giuseppe Greco1 2 Filippo Giannazzo 1 Alessia Frazzetto1 Vito Raineri1 Fabrizio Roccaforte1 Abstract The effects of near-surface processing on the properties of AlGaN GaN heterostructures were studied combining conventional electrical characterization on high-electron mobility transistors HEMTs with advanced characterization techniques with nanometer scale resolution . transmission electron microscopy atomic force microscopy AFM and conductive atomic force microscopy C-AFM . In particular a CHF3-based plasma process in the gate region resulted in a shift of the threshold voltage in HEMT devices towards less negative values. Twodimensional current maps acquired by C-AFM on the sample surface allowed us to monitor the local electrical modifications induced by the plasma fluorine incorporated in the material. The results are compared with a recently introduced gate control processing the local rapid thermal oxidation process of the AlGaN layer. By this process a controlled thin oxide layer on surface of AlGaN can be reliably introduced while the resistance of the layer below increase locally. Introduction Gallium nitride GaN -based heterostructures are promising materials for the fabrication of high-frequency and high-power devices. In particular the presence of spontaneous and piezoelectric polarization charges in AlGaN GaN layers leads to the appearance of a two dimensional electron gas 2DEG at the AlGaN GaN interface typically having sheet carrier densities ns approximately 1 X 1013 cm-2 and high mobility 1 0001 500 cm2 V s 1 . These properties make the materials suitable for the fabrication of transistors based on the 2DEG operating at high frequencies up to tens of gigahertz . .
