[en] Ultrathin and light heterojunction bipolar transistors based on two-dimensional (2D) layered materials with flexible semiconducting properties have been considered for several electronic applications. In this paper, a van der Waals p-BP/n-MoS₂/p-BP BJT is demonstrated. It is fabricated using mechanical exfoliation, where a dry transfer technique is used to stack a vertical double heterojunction. The device structure includes nanoflakes of black phosphorus (BP) and MoS₂. The current–voltage characteristics of the common–emitter and common–base configurations are examined. These p-BP/n-MoS₂/p-BP bipolar transistors exhibit current–voltage characteristics similar to those of conventional p-n-p bipolar transistors. Devices with thin MoS₂ layers show good saturation current–voltage characteristics, and a maximum common–emitter current gain (β  =  I _C/I _B) of approximately 10.1 is obtained at room temperature (300 K). Furthermore, the thickness dependence of the base region (n-MoS₂) is investigated for the common–emitter output electrical characteristics (V _CE  −  I _C) of a double heterojunction bipolar transistor in which the emitter is grounded. The collector current decreases as the thickness of n-MoS₂ is increased. This study can pave the way for the application of 2D materials as controllable amplifiers in flexible electronics. (paper)