A 230-Watt S-band SiGe heterojunction bipolar transistor

Large-area Si/Si/sub 1-x/Ge/sub x/ heterojunction bipolar transistors (HBTs) have been demonstrated with record output power at S-Band. Under pulsed conditions in class C operation, a saturated power in excess of 230 W was achieved at 2.8 GHz. At 200 W the devices exhibited a collector efficiency of 46% and a power gain of 6.9 dB. Devices with implanted Si bases had comparable gain, but only 35% efficiency at 150 W, and saturated at 180 W. In class A operation, 13.5 dB gain was demonstrated at 3.1 GHz on smaller devices. For high f/sub max/, a self-aligned silicided polysilicon-emitter structure was used in conjunction with a graded Si/sub 1-x/Ge/sub x/ base. Variable temperature dc tests and accelerated life tests have indicated no reliability problems. The results indicate for the first time that Si/SiGe HBTs are suitable for high-power, high-frequency applications.