| 摘要 |
<p>The present invention relates to a bipolar power transistor intended for radio frequency applications, especially for use in an amplifier stage in a radio base station, and to a method for manufacturing the bipolar power transistor. The power transistor comprises a substrate (13), an epitaxial collector layer (15) on the substrate (13), a base (19) and an emitter (21) formed in the collector layer (15). The degree of doping Nc(x) of the collector layer varies from its upper surface (24) and downwards to at least half the depth of the collector layer, essentially according to a polynom of at least the second degree, a0 + a1, + a2x2 + ..., where a¿0? is the degree of doping at the upper surface (24); x is the vertical distance from the same surface (24) and a1, a2, ... are constants. The transistor can further comprise an at least approximately 2 νm thick insulation oxide (17) between the epitaxial collector layer (15) and higher situated metallic connections layers (31, 33).</p> |
