In recent years Indium Nitride (InN) has attracted much attention due to the considerable advancement in the growth of high quality crystals. Furthermore, several new works on the material properties proposed a bandgap of 0.7 eV [215],[216],[217] instead of 1.9 eV [4]. Here a Monte Carlo approach is used to investigate the electron transport, considering two band structures [218],[219]. The calculations include the three lowest valleys of the conduction band (depending on the chosen band structure, see Table 3.4) and account for non-parabolicity effects. Several stochastic mechanisms such as acoustic phonon, polar optical phonon, inter-valley phonon, Coulomb, and piezoelectric scattering are considered and their impact is assessed [8]. The parameter values for the acoustic deformation potential (ADP =7.1 eV), polar-optical phonon scattering ( =73 meV or 89 meV), inter-valley scattering ( = ), mass density (=6.81 g/cm), and static and high-frequency dielectric constants ( =15.3 and =8.4) are adopted from [219],[221]. In addition, the influence of another set of dielectric constants ( =11.0 and =6.7) recently proposed in [222] in conjunction with the narrow bandgap and lower effective mass is studied.

Bandgap energy | Electron mass | Non-parabolicity | Scattering models | Ref. | ||||||||

A | ||||||||||||

eV | eV | eV | m | m | m | 1/eV | 1/eV | 1/eV | meV | - | - | |

1.89 | 4.09 | 4.49 | 0.11 | 0.4 | 0.6 | 0.419 | 0.088 | 0.036 | - | - | - | [218] |

1.89 | - | - | 0.11 | - | - | - | - | - | 89 | 15.3 | 8.4 | [176] |

1.89 | 4.09 | 4.49 | 0.11 | 0.4 | 0.6 | 0.419 | 0.88 | 0.036 | 89 | 15.3 | 8.4 | [223] |

1.89 | - | - | 0.11 | - | - | 0.419 | - | - | 89 | 15.3 | 8.4 | [224] |

0.8 | 3.0 | 3.4 | 0.042 | 1.0 | 1.0 | 0.419 | - | - | 89 | 15.3 | 8.4 | [225] |

1.89 |
4.09 | 4.49 | 0.11 | 0.4 | 0.6 | 0.419 | 0.88 | 0.036 | 89 | 15.3 | 8.4 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|

M-L | ||||||||||||

eV | eV | eV | m | m | m | 1/eV | 1/eV | 1/eV | meV | - | - | |

0.69 | 2.47 | 3.399 | 0.04 | 0.25 | 1 | 1.413 | 0 | 0 | 73 | 15.3 | 8.4 | [221] |

0.7 | - | - | 0.07 | - | - | - | - | - | - | 9.3 | 6.7 | [226] |

0.69 |
2.47 | 3.399 | 0.04 | 0.25 | 1 | 1.413 | 0 | 0 | 75/89 | 11.0 | 6.7 |

An accurate piezoelectric scattering model, which accounts for non-parabolicity and wurtzite crystal structure, is also employed [227]. Table 3.5 summarizes experimental values for the elastic constants (, , and ) of wurtzite InN. From these the corresponding longitudinal and transversal elastic constants ( and ) and sound velocities ( and ) are calculated.

Ref. | |||||||

GPa | GPa | GPa | GPa | GPa | ms | ms | |

- | - | - | 265 | 44 | 6240 | 2550 | [176] |

223 | 115 | 48 | 218 | 50 | 5660 | 2720 | [168] |

190 | 104 | 10 | 163 | 23 | 4901 | 1845 | [228] |

271 | 124 | 46 | 248 | 57 | 6046 | 2893 | [167] |

258 | 113 | 53 | 242 | 61 | 5966 | 2987 | [229] |

Table 3.6 gives theoretical values of the piezoelectric coefficients and available in the literature and the calculated corresponding and (= is assumed). Choosing the set of elastic constants from [168] and piezoelectric coefficients from [230] results in a coupling coefficient =0.24.

S. Vitanov: Simulation of High Electron Mobility Transistors