Stochastic Gain Degradation in III-V Heterojunction Bipolar Transistors Due to Single Particle Displacement Damage

As device dimensions decrease, single displacement effects become more important. We measured the gain degradation in III-V heterojunction bipolar transistors due to single particles using a heavy ion microbeam. Two devices with different sizes were irradiated with various ion species ranging from oxygen to gold to study the effect of the irradiation ion mass on gain change. From the single steps in the inverse gain (which is proportional to the number of defects), we calculated cumulative distribution functions to help determine design margins. The displacement process was modeled using the MARLOWE binary collision approximation code. The entire structure of the device was modeled and the defects in the base-emitter junction were counted to be compared with the experimental results. While we found good agreement for the large device, we had to modify our model to reach reasonable agreement for the small device.