Intro -- ABSTRACT -- POPULARVETENSKAPLIG SAMMANFATTNING -- PREFACE -- ACKNOWLEDGEMENT -- Contents -- Part I -- 1.1 Introduction -- 1.2 Fundamental properties of group-III nitride semiconductors -- 1.3 Epitaxy of N-polar III-Nitrides -- 1.4 Characterization techniques -- 1.5 Polarity determination -- 1.6 Summary of main results -- References -- List of abbreviations -- Part II -- 2.1 Publications included in the thesis -- 2.2 Publications not included in the thesis -- Papers.