Device structures and fabrication methods for a bipolar junction transistor. The device structure includes an intrinsic base, an emitter having a vertical arrangement relative to the intrinsic base, and a collector having a lateral arrangement relative to the intrinsic base. The device structure may be fabricated by forming the intrinsic base and the collector in a semiconductor layer, and epitaxially growing the emitter on the intrinsic base and with a vertical arrangement relative to the intrinsic base. The collector and the intrinsic base have a lateral arrangement within the semiconductor layer.