Pulsed measurements on InAlAs/InGaAs HBTs with enhanced performance

The effect of the pulse width and pulse period of the injected base current on the I-V characteristics of InAlAs/InGaAs HBTs with an emitter ledge design is examined. The maximum differential current gain increased to up to 115% with decreasing pulse width while the pulse period did not have a major influence. The gain enhancement in the pulse mode can be attributed in part to less junction heating than the one occurring under DC conditions. Elevated temperature measurements performed on these devices as well as cryogenic measurements indicate a gain difference from room temperature measurements of up to 15% suggesting that the gain increase observed under pulsed conditions is augmented by additional mechanisms. We proposed an additional process upon which the base recombination current under pulsed conditions is reduced leading to gain increase. This observation suggests that HBT operation can be significantly enhanced when the device is operating under pulsed bias