Atomic Force Microscopy Analysis of Orientation Effect on InP-Based Heterojunction Bipolar Transistors

摘要

The InP-based heterojunction bipolar transistors (HBT) are the most promising electron devices for satellite communications and for wireless applications. Unlike the planar silicon technology, in the mesa technology of III-V compound semiconductor heterojunctions a passivating layer is necessary. The presence of this dielectric may cause a high recombination process along the mesa surface, with a great impact on the HBT performance and reliability. In our previous researches (1), we found an abnormal effect in silicon nitride fully passivated InP/InGaAs HBT: the [01-1] emitter orientated HBT shows a considerable degradation of the emitter-base junction characteristics. Many investigations (2-6) have continued this research, however, an understanding of the physical origins of the degradation is still lacking. A high resolution physical characterization must be used. Our work shown the influence of the mesa surface, imaged by Atomic Force Microscopy (AFM), on the current gain of InP/InGaAs heterojunction bipolar transistor for three emitter crystallographic orientations.