The fabrication of Ga/sub 1-x/Al/sub x/As-GaAs heterojunction bipolar transistors for rapid material analysis

We report a procedure for fabricating Ga/sub 1-x/Al/sub x/As-GaAs heterojunction bipolar transistors with a single Al-Ge-Ni metallization step for rapid material analysis. Al-Ge-Ni produces an excellent ohmic contact to both n- and p-type GaAs, and eliminates the need for two metallization steps to produce the three transistor contacts. Complete transistor fabrication, which includes separate etching steps to the base and the subcollector, can be carried out in approximately four hours. We have used this rapid turnaround time to enhance wafer yield by minimizing the lag time between the onset of a growth problem or reactor hardware problem and subsequent growth runs.>