Collector breakdown in the heterojunction bipolar transistor laser

Data are presented on a quantum-well (QW)-based $InGaP∕GaAs∕InGaAs$ (QW) heterojunction bipolar transistor laser modified with external (increased) mirror reflection yielding lower threshold current $(IB=23→19mA)$ and higher collector breakdown voltage $(⩾2.5V)$⁠. Increased breakdown at lower currents is observed on the collector $I-V$ characteristics, at constant base current $IB$⁠, as a slope change, a corner, and a narrow-line to broadband spectral shift from stimulated (high coherent optical field) to spontaneous (lower incoherent field) operation, a consequence of quenching or reducing photon-assisted tunneling (Franz-Keldysh effect) under the constraint $IE+IB+IC=0$ as $α→1(α≡ΔIC∕ΔIE)$⁠.