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 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.

Abstract: A heterojunction bipolar transistor, comprising an elongated base mesa, an elongated base electrode, two elongated emitters, an elongated collector, and two elongated collector electrodes. The elongated base electrode is formed on the base mesa along the long axis of the base mesa, and the base electrode has a base via hole at or near the center of the base electrode. The two elongated emitter are formed on the base mesa respectively at two opposite sides of the base electrode, and each of two emitters has an elongated emitter electrode formed on the emitter. The elongated collector is formed below the base mesa. The two elongated collector electrodes are formed on the collector respectively at two opposite sides of the base mesa.

Abstract: A HBT on a GaAs substrate is presented, wherein its base comprises a first base layer comprising IniGa1-iAs with an Indium content i with a slope s1 and a second base layer on the emitter side comprising InjGa1-jAs with an Indium content j with a slope s2, and an average of s1 is half of the average of s2 or smaller; or the base comprises a first base layer comprising InmGa1-mAs with an Indium content m and a second base layer on the emitter side comprising InnGa1-nAs with an Indium content n, and an average of n is larger than the m at a second base layer side; or the base comprises a first base layer pseudomorphic to GaAs with a bulk lattice constant larger than GaAs, and the emitter comprises a first emitter layer pseudomorphic to GaAs with a bulk lattice constant smaller than GaAs.

Abstract: A heterojunction bipolar transistor, comprising an elongated base mesa, an elongated base electrode, two elongated emitters, an elongated collector, and two elongated collector electrodes. The elongated base electrode is formed on the base mesa along the long axis of the base mesa, and the base electrode has a base via hole at or near the center of the base electrode. The two elongated emitter are formed on the base mesa respectively at two opposite sides of the base electrode, and each of two emitters has an elongated emitter electrode formed on the emitter. The elongated collector is formed below the base mesa. The two elongated collector electrodes are formed on the collector respectively at two opposite sides of the base mesa.

Abstract: A heterojunction bipolar transistor, comprising an elongated base mesa, an “H” shaped emitter, two base electrodes, an elongated collector, and two elongated collector electrodes. The “H” shaped emitter is formed on the base mesa and has two parallel bars connected by a cross-bar. Two elongated emitter electrodes are formed respectively on the two parallel bars of the “H” shaped emitter. The “H” shaped emitter has two recesses respectively on two opposite sides of the cross-bar between the two parallel bars. The two base electrodes are formed on the base mesa respectively at the two recesses of the “H” shaped emitter, each of which has a base via hole near a center of the base mesa. The elongated collector is formed below the base mesa. The two elongated collector electrodes are formed on the collector respectively at two opposite sides of the base mesa.

Abstract: A HBT on a GaAs substrate is presented, wherein its base comprises a first base layer comprising IniGa1-iAs with an Indium content i with a slope s1 and a second base layer on the emitter side comprising IniGa1-jAs with an Indium content j with a slope s2, and an average of s1 is half of the average of s2 or smaller; or the base comprises a first base layer comprising InmGa1-mAs with an Indium content m and a second base layer on the emitter side comprising InnGa1-nAs with an Indium content n, and an average of n is larger than the m at a second base layer side; or the base comprises a first base layer pseudomorphic to GaAs with a bulk lattice constant larger than GaAs, and the emitter comprises a first emitter layer pseudomorphic to GaAs with a bulk lattice constant smaller than GaAs.

Abstract: A heterojunction bipolar transistor, comprising an elongated base mesa, an “H” shaped emitter, two base electrodes, an elongated collector, and two elongated collector electrodes. The “H” shaped emitter is formed on the base mesa and has two recesses respectively on two opposite sides of the “H” shape, and the emitter has two elongated emitter electrodes formed on the “H” shaped emitter. The two base electrodes are formed on the base mesa respectively at the two recesses of the “H” shaped emitter, and each of the base electrodes has a base via hole at or near the center of the base mesa. The elongated collector is formed below the base mesa. The two elongated collector electrodes are formed on the collector respectively at two opposite sides of the base mesa.

Abstract: A heterojunction bipolar transistor, comprising an elongated base mesa, an elongated base electrode, two elongated emitters, an elongated collector, and two elongated collector electrodes. The elongated base electrode is formed on the base mesa along the long axis of the base mesa, and the base electrode has a base via hole at or near the center of the base electrode. The two elongated emitter are formed on the base mesa respectively at two opposite sides of the base electrode, and each of two emitters has an elongated emitter electrode formed on the emitter. The elongated collector is formed below the base mesa. The two elongated collector electrodes are formed on the collector respectively at two opposite sides of the base mesa.