Re: about bjt
In a lateral device, electron flows "laterally" from the emitter to the collector. The base width is define by photolithography therefore beta and ft for these device are poor. In addition, the base resistance is high because connection to the active base in made laterally through a long p-region.
In a verticle device, electron flow downward or vertically from the emitter to the collector. The base is defined by profile engineering of the emitter/base/collector diffusion/implant regions. Thus beta and ft are much higher for these devices, and they also exhibit lower base resistance from their lateral counterparts.