Analysis of base recombination effect in very high maximum oscillation frequency silicon-germanium heterojunction bipolar transistors

The performance for current gain (β) and cutoff frequency (∫ _i) for very high maximum oscillation frequency (∫_max) NPN Si/SiGe/Si Double Heterojunction Bipolar Transistors (SiGe DHBTs) has been analyzed. The simulation results for a conventional Box-Germanium (BT-GE) profile and a Box-Triangular-Germanium (BT-GE) profile are compared in the present work. The Ge profile is kept under the critical thickness limit constraint in both the cases, The BT-GE SiGe DHBT shows a superior current gain and cut-off frequency in comparison with B-GE DHBT. The analysis of the stated observation brings out the dominance of base region recombination in high ∫_max SiGe HBTs, as the base resistance is reduced.