Mitigate the variation of energy band gap with electric field induced by quantum confinement Stark effect via a gradient quantum system for frequency-stable laser diodes

Most light-emitting devices based on quantum-confined structures are commonly utilized as electrically injected devices. However, the electric-field-dependent energy band gap induced by the quantum confinement Stark effect (QCSE) usually hinders the realization of frequency-stable laser devices. This is because the change in the energy band gap, which also means the corresponding change in the photon energy, will result in an electric-field-dependent frequency. Here, we propose a novel approach to mitigate this electric-field-dependent variation in the energy band gap by employing a gradient quantum system. In this system, the energy band edges are inclined due to the action of the indium (In)-segregation effect. This special design can effectively weaken the changes in the band profile associated with the electric field effect and counteract the electric-field-dependent band gap variations within the active region to a certain extent. Experimental studies indicate that the energy band gap of this gradient quantum system remains almost unchanged (<18.9 μeV cm²/A) even under a relatively strong applied electric field. Meanwhile, compared with the traditional GaAs quantum well, the efficiency improvement in the band gap stability of our nanowire–well gradient system is 64.1 % and 70.6 % for the TE and TM polarization modes, respectively, which suggests that our proposed gradient quantum structure can significantly mitigate the electric-field-induced change in the energy band gap. This achievement is of great significance for advancing the development of high-performance frequency-stable laser devices in some advanced fields, such as quantum sensing systems and optical communications.