High-Temperature Stability Base Ohmic Contacts for InP/GaAsSb DHBTs

In today’s telecommunications landscape, the need for transistors capable of efficiently handling high power levels at elevated frequencies is paramount. However, these demands present significant hurdles, particularly concerning transistor reliability when devices are required to operate at or near their peak performance levels. In this context, the thermal stability of ohmic contacts in InP/GaAsSb DHBs has to be investigated and improved. We investigated the stability of several ohmic contact stacks on $\boldsymbol{p}$-doped GaAsSb in terms of their resistivity and stability of RF performance of InP/GaAsSb DHBTs subjected to sequential high-temperature annealing isochronal cycles. A Pt/Ir/Pt/Au stack shows the lowest resistance, the highest $f_{\text {max }}$ and little to no performance degradation when devices are annealed up to $350^{\circ} \mathrm{C}$. TLM contact resistance measurements do not accurately reflect actual RF performance levels.