Bipolar transistor with graded base layer

A method of fabricating a heterojunction bipolar transistor, comprising the steps of:

• a) growing a base layer comprising gallium, indium, arsenic and nitrogen over an n-doped GaAs collector layer from a gallium, indium, arsenic, and nitrogen source, wherein the base layer is p-doped with carbon from an external carbon source;
• and
• b) growing an n-doped emitter layer over the base layer.

A material comprising gallium, indium, arsenic, and nitrogen, wherein the material is doped with carbon at a concentration of about 1.5×1019 cm −3 to about 7.0×1019 cm−3.

A material comprising gallium, indium, arsenic, and nitrogen, wherein the composition of the material is represented by the formula Ga1-xInxAs1-yNy, wherein x and y are each, independently, linearly graded from a larger value at a first surface of the material to a smaller value at a second surface of the material.

A material comprising gallium, indium, arsenic, and nitrogen, wherein the composition of the material is represented by the formula Ga1-xInxAs1-yNy, wherein x is linearly graded from a larger value at a first surface of the material to a smaller value at a second surface of the material and y remains essentially constant throughout the material.

A method of forming a graded semiconductor layer having an essentially linear grade of band gap and an essentially constant doping-mobility product, from a first surface through the layer to a second surface, comprising the steps of:

• a) comparing the doping-mobility product of calibration layers, each of which is formed at a distinct flow rate of one of either an organometallic compound depositing an atom from Group III or V of the Periodic Table, or of a carbon tetrahalide compound depositing carbon, whereby the relative organometallic compound and carbon tetrahalide flow rates required to form an essentially constant doping-mobility product are determined;
• and
• b) flowing the organometallic and carbon tetrahalide compounds over a surface at said relative rates to form an essentially constant doping-mobility product, said flow rates changing during deposition to thereby form an essentially linear grade of band gap through the graded semiconductor layer.