Patent ID: 8906758

Claim:
A method for fabricating an integrated device having a first heterojunction bipolar transistor (HBT) device formed on a first region of a substrate and a second HBT device formed on a second region of the substrate, the first region spaced apart from the second region, the method comprising: depositing a first subcollector layer on the first region and the second region of the substrate to a first subcollector thickness; depositing a first collector layer made of a first group III-V chemical compound above the first subcollector layer to a first collector thickness, the first collector layer having a first collector doping level in order to meet a first predetermined breakdown voltage and a first predetermined cut-off frequency of the first HBT device; etching the first subcollector layer and the first collector layer above the second region of the substrate to create an opening that exposes the second region of the substrate; depositing a second subcollector layer on the second region of the substrate to a second subcollector thickness that is different than the first subcollector thickness; depositing a second collector layer made of a second group III-V chemical compound above the second subcollector layer to a second collector thickness that is different from the first collector thickness such that a sum of the first subcollector thickness and the first collector thickness is equal to a sum of the second subcollector thickness and the second collector thickness, the second collector layer having a second collector doping level in order to meet a second predetermined breakdown voltage and a second predetermined cut-off frequency of the second HBT device which are different from the first predetermined breakdown voltage and the first predetermined cut-off frequency of the first HBT device, the second collector layer occupying a portion of the opening, the second collector doping level being different from the first collector doping level; etching the first collector layer and the first subcollector layer to define the first HBT device such that an entire bottom surface of the first collector layer contacts an entire top surface of the first subcollector layer; and etching the second collector layer and the second subcollector layer to define the second HBT device such that an entire bottom surface of the second collector layer contacts an entire top surface of the second subcollector layer.