Heterojunction III-V transistor, in particular HEMT field effect transistor or heterojunction bipolar transistor

A bipolar heterojunction transistor comprising:

• a III-V semiconductor material having a broad forbidden band comprised of a III-V compound containing gallium as one of its III elements and both arsenic and nitrogen as V elements, the nitrogen content being less than about 5%, and the broad forbidden band material forms the emitter of the transistor;
• and
• a III-V semiconductor material having a narrow forbidden band comprised of at least a fourth III or V element, wherein said fourth element permits adjustment of the width of the forbidden band, the conduction band discontinuity ΔEc, and the valance band discontinuity ΔEv of the heterojunction, wherein the narrow forbidden band material forms the base of the transistor and wherein the fourth element is indium, substituted for gallium, at a fraction of no more than about 10% so as to obtain a forbidden band of about 0.8 eV to 1 eV, and in that the broad forbidden band material is GaInP with an indium content of about 50% so as to obtain a ΔEv discontinuity of about 450 meV.