Investigation Of The Magnetotransport Properties Of The 2DEG In AlGaN/AlN/GaN Structure

Owing to their advantages such as wide bandgap, high breakdown field and high electron saturation velocity.â…¢-nitride materials are an ideal candidates for high power microwave devices. Among thoseâ…¢-nitride materials, AlGaN/GaN heterostructures are the new low-dimensional semiconductor material structure with large conduction-band offset and strong polarization-induced electric field. Subsequently, several experimental studies show that the insertion of the thin AlN interlayer resultes in an improvement of electrical properties. A detail study on the transport properties of the 2DEG in AlGaN/AlN/GaN heterostructures is very important in the development of the low-dimensional semiconductor physics.The magnetoresistance oscillations of semiconductor heterojunction two -dimensional electron gas(2DEG) originate from electron quantum effect, which reflecting the state density variation of Landau energy at Fermi level.We can study the magnetoresistance oscillations of two—dimensional electron gas by magnetotransport measurement, by which we can get abundant electrical character and electrons—subband property.In this dissertation, AlGaN/AlN/GaN heterostructures have been fabricated by metal-organic chemical vapor deposition(MOCVD). Hall bar has been made by means of Stepper Scanning Photo etching Machine by three times. Ti/Al/Ni/Au Metals were evaporated by using electron beam evaporation method on the sample's surface.After annealing alloy, ohms contact was formed. Standard,low frequency and low current, lock-in techniques were used.First,Transport measurements were used to characterize AlGaN/AlN/GaN/SiC at different temperatures. While the carrier concentration, n=1.32×1013 cm^-2, remained relatively unchanged from 300K down to 2 K, the mobility increased from 1672 to 11237 cm² /Vs.Shubnikov-de Haas oscillations were observed in fields as low as 2.5 T at 2K. Despite the high n, quantum Hall plateaus.Effective-mass values of the 2DEG in the triangular quantum well at the heterointerfaces are obtained by analyzing the temperature-dependent Shubnikov-de Haas(SdH) oscillations. The ratio of the transport lifetime to the quantum scattering time is often evaluated to gain information on the dominant scattering mechanism.This ratio was 9 in our sample, indicating that small-angle scattering is important in this structure.