![]() ![]() A hetero bipolar transistor comprising: a semiconductor substrate a first semiconductor layer formed on the semiconductor substrate and comprised of a crystal containing silicon and germanium a second semiconductor layer formed on the first semiconductor layer and comprised of a crystal containing silicon and germanium, at least a portion of the second semiconductor layer functioning as a base layer and a third semiconductor layer formed on the second semiconductor layer and comprised of a crystal containing silicon, at least a portion of the third semiconductor layer functioning as an emitter layer, wherein the second semiconductor layer includes a region having a germanium composition ratio that varies stepwisely with a difference of 2.5% or more, in the vicinity of a boundary between the first semiconductor layer and the second semiconductor layer.ģ. A hetero bipolar transistor comprising: a semiconductor substrate a first semiconductor layer formed on the semiconductor substrate and comprised of a crystal containing silicon and germanium a second semiconductor layer formed on the first semiconductor layer and comprised of a crystal containing silicon and germanium, at least a portion of the second semiconductor layer functioning as a base layer and a third semiconductor layer formed on the second semiconductor layer and comprised of a crystal containing silicon, at least a portion of the third semiconductor layer functioning as an emitter layer, wherein the second semiconductor layer includes regions each having a germanium composition ratio that varies stepwisely with a difference of 2.5% or more, in the vicinity of a boundary between the first semiconductor layer and the second semiconductor layer and a boundary between the second semiconductor layer and the third semiconductor layer.Ģ.
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