Patent ID: 6946355

Claim:
A method for the production of a hetero-bipolar transistor having an emitter composed of several layers in a mesa structure, and a ledge that projects laterally beyond the mesa structure comprising the steps of: a) depositing a first emitter layer on a base layer, composed of a layer sequence of semiconductor layers deposited over an area; b) covering said first emitter layer with a stop layer that can be etched; c) depositing at least one metallic contact layer; d) depositing at least one dielectric cover layer which serves in a structured manner as a first mask for producing the emitter mesa structure; e) forming a metallic emitter contact in said at least one metallic contact layer by underetching said at least one dielectric cover layer; f) etching of the emitter mesa structure up to said stop layer using a material selective etching process; g) depositing at least one passivation layer; h) structuring said at least one passivation layer using said at least one dielectric cover layer as a second mask for defining a ledge region; i) etching a ledge, wherein said at least one passivation layer forms a third mask, and wherein said etching said ledge uses an isotropic etching method down to said base layer.