Further Suppression of Surface-Recombination of an InGaP/GaAs HBT by Conformal Passivation

Conformal passivation on an InGaP/GaAs HBT with significant reduction in the base surface-recombination effect is demonstrated. Not only dc behaviors but also RF performances are remarkably improved compared with the conventional emitter-ledge structure. Based on the conformal passivation, i.e., the base surface is covered by the depleted InGaP ledge structure and sulfur ((NH
₄
)
₂
S
_x
) treatment, lower base surface-recombination current density, lower specific contact resistance, lower sheet resistance, higher current gain, higher collector current, and higher maximum oscillation frequency are obtained