Atomic layer epitaxy grown heterojunction bipolar transistor having a carbon-doped base

Carbon was incorporated into the base of a GaAs/AlGaAs HBT (heterojunction bipolar transistor) in a novel way using atomic layer epitaxial (ALE) growth from a trimethylgallium (TMG) source. The p -type doping results from the formation and subsequent incorporation of the partially cracked TMG in the form of metal carbide under the specific ALE growth conditions used. The AlGaAs emitter and GaAs collector of the HBT were grown by conventional organometallic chemical vapor deposition (OMCVD), while the base region was grown by ALE. Transistors with current gains greater than 100 were obtained at low current densities of 1300 A-cm^-2. This value of the gain implies a minority-carrier diffusion length of 1.4 μm. This is typical of conventionally grown HBTs, indicating that the low growth temperature used for ALE does not degrade the minority-carrier transport properties of the material