Characteristics of substrate-induced low frequency oscillations in GaAs HBT devices and circuits
Spurious oscillations in the low frequency region (below 100kHz) were investigated in InGaP/GaAs HBT devices and circuits. These low frequency oscillations (LFOs) are predominantly activated by the field across the semi-insulating GaAs substrate located between the subcollector and backside metal (of an emitter-up device). Several experiments were conducted to control and eliminate LFOs by floating the backside potential or applying a voltage to the backside metal. In both cases, the electric field across the GaAs substrate is minimized, thereby reducing the mechanism of the field-enhanced capture of electrons by traps in this region.