This work deals with the realization of resonant tunneling diodes based on polar and non-polar gallium nitride for use in very high frequency applications. First, the material properties of gallium nitride and aluminium nitride are discussed. After a brief review of existing theories for the calculation of heterostructures, results of simulations on some proposed structures are presented. The growth and fabrication of several single and dual quantum barrier diode structures using MOCVD and clean room contact lithography are then described. The fabricated diodes were electrically measured and characterised. The results obtained are finally compared with the literature.