Abstract: The invention concerns a heterojunction bipolar transistor comprising a support, and epitaxially grown from said support, at least: one collecting, respectively emitting, layer; at least one base layer; and at least one emitting, respectively collecting, layer. The collecting, respectively emitting, layer comprises: at least one first undercoat contacted with said base layer, substantially of similar composition as said emitting, respectively collecting, layer; and at least one second undercoat on the side opposite said base layer relative to said first undercoat.

Abstract: The invention concerns a heterojunction bipolar transistor comprising a support, and epitaxially grown from said support, at least: one collecting, respectively emitting, layer; at least one base layer; and at least one emitting, respectively collecting, layer. The collecting, respectively emitting, layer comprises: at least one first undercoat contacted with said base layer, substantially of similar composition as said emitting, respectively collecting, layer; and at least one second undercoat on the side opposite said base layer relative to said first undercoat.

Abstract: Electronic circuits dedicated to high frequency and high power applications based on gallium nitride (GaN) suffer from reliability problems. The main reason is a non-homogenous distribution of the electronic density in these structures that originates from alloy disorders at the atomic and micrometric scale. This invention provides processes for manufacturing semiconducting structures based on nitrides of Group III elements (Bal, Ga, In)/N which are perfectly ordered along a preferred crystalline axis. To obtain this arrangement, the ternary alloy barrier layer is replaced by a barrier layer composed of alternations of binary alloy barrier layers. The lack of fluctuation in the composition of these structures improves electron transport properties and makes the distribution more uniform.