Patent ID: 7019383

Claim:
A gallium arsenide heterojunction bipolar transistor, said transistor comprising a collector layer; a first spacer layer situated over said collector layer, said first spacer layer being a high-doped P+ layer, said first spacer layer having a first concentration of a P type dopant; a base layer situated over said first spacer layer, said base layer having a second concentration of said P type dopant, wherein said base layer includes nitrogen for facilitating a decrease of a turn-on voltage, wherein said first spacer layer prevents said nitrogen from causing a decrease in a DC current gain of said transistor, wherein said base layer includes a concentration of indium that is linearly graded in said base layer, wherein said concentration of indium causes a decrease in an energy level of a conduction band to occur at a base-collector transition, wherein said first concentration of said P type dopant in said first spacer layer counteracts said decrease in said energy level of said conduction band at said base-collector transition; an emitter layer situated over said base layer; wherein said first concentration of said P type dopant is greater than said second concentration of said P type dopant, wherein said P type dopant comprises carbon.