Electrical characterization of an interface n‐type conduction channel in cubic GaN/AlGaN heterostructures

Abstract

AbstractWe report on the growth of non‐polar cubic GaN/AlxGa1‐xN heterostructures by plasma‐assisted molecular beam epitaxy on free standing (001) 3C‐SiC substrates. The samples consist of 600 nm thick GaN buffer and 30 nm AlxGa1‐xN layer. The growth was observed by in‐situ reflection high energy electron diffraction (RHEED). Layer thickness was determined by AlxGa1‐xN RHEED growth oscillations and by reflectance measurements after growth. The morphological and the structural properties are analyzed by high resolution x‐ray diffraction (HRXRD) and atomic force microscopy (AFM). Using a metal oxide semiconductor heterostructure (MOSH), capacitance voltage (CV) characteristics were measured. The oxide layer consists of SiO2, the thickness was varied between 15 nm and 30 nm. SiO2 layer was produced by plasma enhanced chemical vapour deposition (PECVD). The contact structure is lithographically deposited on top of the sample. Metal contacts have a diameter of 300 μm and were thermally evaporated consisting of 15 nm Ni and 50 nm Au. By CV measurements of the MOSH structures we obtain clear evidence for the existence of an electron accumulation layer at the GaN/AlGaN interface. The sheet carrier concentration at the hetero‐interface is calculated from experimental data (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)