Low-frequency drain noise in AlGaN/GaN HEMTs on Si substrate

Abstract

ABSTRACT This paper deals with the analysis of the low frequency drain noise in gallium nitride FET on silicon substrate. The dispersion of LF noise level is detailed and the drain current noise is compared for devices with gate length of 1.5µm and 3.5 µm. We discuss two types of noise mechanisms both used as a diagnostic tool: generation-recombination noise and 1/f noise. Measurements in saturation regime have revealed g-r noise mechanism correlated with the activation of surface states in access regions. On the basis of the 1/f normalized noise, i.e. the H /N parameter, GaN HEMT on silicon have demonstrated as low LF noise as GaAs based transistors. Key words: AlGaN/GaN HEMT, LF drain noise, 1/f noise, g-r noise 1. INTRODUCTION HEMTs based on wide bandgap compound semiconductors potentially present attractive performances for high power, high temperature and high frequency applications. The performances of GaN FETs take benefit of high peak and saturation velocities and high sheet carrier density. Different substrates have been used for the growth of GaN based structures and include sapphire, silicon carbide and silicon. It appears that sapphire and SiC substrates are more largely used than Si for GaN HEMT. Nevertheless, Si substrate offers new possibilities such as large size wafer, low-cost, highly perfect substrates and good thermal properties. The low frequency noise level is a key parameter of microwave devices, since it limits the performance of wide bandwidth circuits, oscillators, mixers and other non-linear circuits in which such noise is up-converted to the microwave range. Also, it is well known that LF noise analysis is used as a quality indicator of epitaxial structures and is very efficient to detect crystal defects