Passivation of InP-based HBTs

The passivation of the exposed semiconductor surfaces in a device is necessary to ensure good device performance. In this study we examine how different surface treatments and geometric device designs can be used to improve the dc performance of InP-based heterostructure bipolar transistors. We show how sulphur and UV-ozone treatment improves the performance of large-area devices and illustrate the effects of the treatment through XPS measurements on the semiconductor surfaces. We also demonstrate that a combination of UV-ozone+HF can lead to improved performance of small, high-frequency devices. This approach is contrasted with results using a layer structure with a thin emitter, where the emitter is left on the device to self-passivate the base surface. In this case the thin emitter layer on the base is depleted and no passivation treatment is needed.