Bipolar transistor
AssigneeNEC Corporation
InventorNoriaki Matsuno
Life of this patent
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Abstract
In a bipolar transistor including a base layer made of SiGe, a non-doped SiGe layer and a non-doped Si layer are provided between the base layer and an emitter layer. The composition ratio of Ge in the emitter side of SiGe base layer is decreased with increasing proximity to the emitter side, and the composition ratio of Ge in the non-doped SiGe layer is made smaller than the composition ratio of Ge at the emitter layer-side end of the SiGe base layer. In this manner, restriction is put on the diffusion of boron from the base layer to the emitter side, and the base-emitter junction capacitance CBE reduced. Furthermore, the direct-current gain β can be improved by increasing the composition of Ge at the emitter end of the SiGe base layer to more than or equal to a predetermined value.
Claims16
A bipolar transistor comprising:
- a laminated structure comprising:
- a collector layer;
- a SiGe base layer;
- a non-doped SiGe layer;
- a non-doped SiGe layer;
- and
- an n-type emitter layer, in that order,
- wherein a composition ratio of Ge gradually decreases with increasing proximity to an emitter layer side in at least a part of an emitter layer side of the SiGe base layer, and a composition ratio of Ge in the non-doped SiGe layer is smaller than a composition ratio of Ge at an emitter-side end of the SiGe base layer.
A bipolar transistor comprising:
- a laminated structure comprising:
- a collector layer;
- a SiGe base layer;
- a non-doped SiGe layer;
- a non-doped Si layer;
- and
- an n-type emitter layer, in that order,
- wherein a composition ratio of Ge stepwise deceases with increasing proximity to an emitter layer side in at least a part of an emitter layer side of the SiGe base layer, and a composition ratio of Ge in the non-doped SiGe layer is smaller than a composition ratio of Ge at an emitter layer-side end of the SiGe base layer.
Dependencies are inferred from the claim text.