Models Of Compensation Ratio And Mobility Of Wurtzite N-GaN

The room temperature carrier Hall mobility of wurtzite n-GaN as a function ofcarrier concentration for different compensation ratio, given by Chin et al.theoretically using the variational method, is usually used to evaluate thecompensation ratio. However, the compensation ratio based on Chin's theory,sometimes diviate much from value through theoretically fitting of temperaturedependent Hall effect measurements. Even more, the figure of mobility dependingon carrier concentration and compensation ratio given by Chin et al didn't give thefomular of compensation ratio. To solve this problem, two compensation ratiocalculation models based on Chin's theory and carder scattering theory respectivelyare given in this work. The mobility calculation model and the compensation ratiocalculation model both for 77K wurtzite n-GaN samples are also given in this workbased on Chin's theory. Besides, the mobility of wurtzite n-GaN as a function ofcarrier concentration for different dislocations,and the lattice mismatch between theGaN epitaxy and substrate are analysed. The results show that1. The calculation of compensation ratio at room temperature for wurtzite n-GaNsamples should be different from strictly unintentionally doped GaN and Si-dopedGaN. For the strictly unintentionally doped GaN, an analytical model forcompensation ratio at room temperature given by this work, agrees well with Chin'stheory in wide concentration(10¹⁶-10²⁰cm^-3)ranges. A comparison between thesemodels' value and the fitting value from experimental results show that the newanalytical models also have a good agreement in the electron concentration ranges of10¹⁶-10²⁰cm^-3and 3×10¹⁶-10¹⁸cm^-3for strictly unintentionally doped GaN andSi-doped GaN, respectively.It's the unintentionally dopants such as silicon andoxygen that should be taken for increasing donor concentration as well as decreasingcompensation ratio under high temperature praparation.2. The compensation ratio calculation model for 77K wurtzite n-GaN samplesagrees well with the value decided from theoretically fitting of temperature dependentHall effect measurements and that of Chin's theory in wide concentration (10¹⁶-10¹⁹cm^-3)ranges, nomatter whate the samples are strictly unintentionally doped orSi-doped GaN. It indicates that silicon is a high effective dopant in GaN and play aimportant role in decreasing compensation ratio only at high temperature. 3. The mobility depend on edge dislocation concentration, screw dislocationconcentration as well as the interaction between them. The models of mobility ofwurtzite n-GaN as a function of carrier concentration for different dislocations isplausibility and previded with disunity, and should be improved.4. The analyse of lattice mismatch between GaN epitaxy and substrate indicatesthat the atoms along with wideth of rectangle crystal lattice take precedence to matchatoms in another two-dimensional crystal lattice, not affected by the atoms along withlength.