Transport Properties Of 2-Dimensional Electron Gas In AIGaN/GaN Heterostructures

In recent years, GaN-based wide-band-gap â…¢-V nitride semiconductors areattracting extensive interest for their potential for optoelectronics devices appli-cation The large band gap of 3 39eV and the direct bad gap structure make GaNthe ideal material in fabricating optoelectronics devices working in the blue andultraviolet wavelength, such as blue light-emitting diodes and lasers And due tothe high breakdown field (~200V) and saturated drift velocity (~27x 10~7 cm/s),this material can be used in fabricating high-power/high-frequency devices, suchas GaN-based HBT and HEMT Furthermore, the wurtzite polytypes of GaN,AlN, and InN form a continuous alloy system whose direct band gaps range from19eV for InN, to 3 4eV for GaN, to 6 2eV for AlN It is this wide range of directband gaps, covering nearly the whole visible spectrum and the ultraviolet, thatmakes them so attractive for fabricating optoelectronics devices which are activeat wavelengths ranging from the red well into the ultravioletIn the past few years, notable advances have been made in the GaN-basedmaterial growth and device fabrication Very efficient light-emitting diodes, bluelasers short-length GaN-based heterostructure field effect translstors, GaN-basedsuperIattices, and quantum wells, have been reported With regard to theoreticalstudies, as early as 1975 Littlejohn et al performed a calculation of mobilityand electron velocity in GaN by using a single-valley Monte Carlo model Dasand Ferry calculated the average electron velocity of GaN assuming a Maxwelhandistribution Gaskill made an investigation on Hall mobility of GaN based on thecontraction mapping solution of Boltzmann equation Recently some work is doneabout the steady-state e1ectron transport ln bulk GaN by ensemble MC technlqueThe transport propert1es of two-dlmenslonal electron gas at the Al.Ga,--.N/GaNlnterface have been slmulated, tooIn the mlddle of 1980's, a non-Boltzmann approach was developed by Lel andTlng to nonllnear transport for electron-phonon-lmpurlty systems ln the presenceof a strong electr1c field Thls method ls based upon a separatIon of the center-of mass mot1on from the relat1\e mot1ol1 of electrons Startlng from the L1ouv1lleEq fOr the denslty matrlx, a force balance equat1on and an energy ba1ance equa-tlon are obta1ned In the 1owest order of e1ectron-phonon and electron-1mpur1tycoupllng but arbltrarlly strong e1ectrlc field An electron temperature ls lntro-duced at the thermodynamlc temperature of the (decoupled) relatlve electronsystem x,'hen lt reaches equll1br1um state The fOrmulat1on has been proved use-ful and convenlent fOr study1ng carrler transport In thls thesls, we apply thebalance equatlon theory to study the llnear and non11near transport of the quas1-2-dlmens1onal electron gas 1n AIGaN/GaN heterostructures...