Negative differential resistance, self-oscillations, and light emission in transistor-injected quantum cascade structures

Abstract We experimentally demonstrate negative differential resistance, collector current oscillations, and light emission in a transistor-injected quantum cascade structure. Distinct transport regimes are accessed by varying the reverse bias across the base-collector junction while independently controlling emitter injection. The collector current shows pronounced oscillations and alternating high–low levels as the reverse bias changes, indicating quantum transport through the superlattice. Oscillations at a peak frequency of 3.2 MHz occur within high-bias negative differential resistance regions. Spontaneous short-wave infrared (SWIR) emission from the base region is characterized using Fourier transform infrared spectroscopy, revealing a peak wavelength of 1.58 $$\mu $$ m. Coupling between the emitted light and superlattice modes is confirmed by SWIR intensity oscillations synchronized with collector current oscillations. Under forward bias of the base-collector junction, the device emits coherent SWIR light at 1.58 $$\mu $$ m, aided by carrier confinement from a quantum impedance matching region. Additionally, spontaneous mid-wave infrared emission is observed from the quantum cascade structure. This three-terminal, transistor-injected platform integrates electronic modulation with tunable optical output, showing promise for a versatile alternative to conventional two-terminal quantum cascade devices that could enable new opportunities in long-wavelength photonics for sensing, communication, and spectroscopy applications.