Measurements of the emitter-injection efficiency and calculations of the emitter effective surface-recombination velocity are reported for polysilicon emitter transistors, i.e., bipolar transistors with a polysilicon–insulator tunnel-junction contact to the emitter. It is demonstrated that the emitter-injection efficiency increases significantly and the emitter effective surface-recombination velocity decreases by two orders of magnitude when a thin insulating layer is deliberately grown between the monocrystalline emitter surface and the polycrystalline contact.