Abstract: A bipolar transistor includes a substrate, a sub-collector layer, a collector layer, a base layer, an emitter layer, a passivation layer, and a collector electrode. The sub-collector layer is formed over the substrate. The collector layer is formed over the sub-collector layer. The base layer is formed over the collector layer. The emitter layer is formed over the base layer. The passivation layer is formed over the substrate and covering a sidewall of the collector layer. The collector electrode is connected to the sub-collector layer through an opening in the passivation layer. The opening exposes at least a portion of the sub-collector layer.

Abstract: A heterojunction bipolar transistor includes: a substrate; a base mesa disposed on the substrate, wherein the base mesa includes a collector layer and a base layer disposed on the collector layer, and wherein in a top view, the base layer includes a first edge and a second edge opposite to the first edge; an emitter layer disposed on the base layer; a base electrode disposed on the substrate and connected to the base layer; a dielectric layer disposed on the base electrode, wherein a first via hole is formed in the dielectric layer at the first edge of the base layer, and a second via hole is formed in the dielectric layer at the second edge of the base layer; and a conductive feature disposed on the dielectric layer, wherein the conductive feature is connected to the base electrode through the first via hole and the second via hole.

Abstract: A heterojunction bipolar transistor includes a bottom sub-collector layer formed over a substrate. The heterojunction bipolar transistor also includes an upper sub-collector layer formed over the bottom sub-collector layer. The heterojunction bipolar transistor also includes a collector layer formed over the upper sub-collector layer. The heterojunction bipolar transistor also includes a base layer formed over the collector layer. The heterojunction bipolar transistor also includes an emitter layer formed over the base layer. The heterojunction bipolar transistor also includes a passivation layer covering the bottom sub-collector layer, the upper sub-collector layer, the collector layer, the base layer, and the emitter layer. The heterojunction bipolar transistor also includes a collector electrode that covers the portion of the passivation layer that is over the sidewall of the upper sub-collector layer.

Abstract: A heterojunction bipolar transistor includes a bottom sub-collector layer formed over a substrate. The heterojunction bipolar transistor also includes an upper sub-collector layer formed over the bottom sub-collector layer. The heterojunction bipolar transistor also includes a collector layer formed over the upper sub-collector layer. The heterojunction bipolar transistor also includes a base layer formed over the collector layer. The heterojunction bipolar transistor also includes an emitter layer formed over the base layer. The heterojunction bipolar transistor also includes a passivation layer covering the bottom sub-collector layer, the upper sub-collector layer, the collector layer, the base layer, and the emitter layer. The heterojunction bipolar transistor also includes a collector electrode that covers the portion of the passivation layer that is over the sidewall of the upper sub-collector layer.

Abstract: A bipolar transistor includes a substrate, a sub-collector layer, a collector layer, a base layer, an emitter layer, a passivation layer, and a collector electrode. The sub-collector layer is formed over the substrate. The collector layer is formed over the sub-collector layer. The base layer is formed over the collector layer. The emitter layer is formed over the base layer. The passivation layer is formed over the substrate and covering a sidewall of the collector layer. The collector electrode is connected to the sub-collector layer through an opening in the passivation layer. The opening exposes at least a portion of the sub-collector layer.

Abstract: A bipolar transistor includes an upper sub-collector layer, a collector layer, a base layer, an emitter layer, and a collector electrode. The collector layer is disposed on the upper sub-collector layer. The base layer is disposed on the collector layer. An emitter layer is disposed on the base layer. The collector electrode is disposed directly on a sidewall of the upper sub-collector layer.

Abstract: A bipolar transistor includes an upper sub-collector layer, a collector layer, a base layer, an emitter layer, and a collector electrode. The collector layer is disposed on the upper sub-collector layer. The base layer is disposed on the collector layer. An emitter layer is disposed on the base layer. The collector electrode is disposed directly on a sidewall of the upper sub-collector layer.