Electroluminescence of 1.65 μm near-infrared wavelength quantum cascade lasers using Si/CaF2 heterostructures

We have demonstrated a room temperature near-infrared electroluminescence (EL) at a wavelength of λ = 1.65 μm from Si/CaF 2 quantum cascade laser structure. Five periods of the active layer were epitaxially grown on an n-Si (111) layer of a silicon-on-insulator (SOI) substrate, forming a single-mode propagation waveguide in transverse magnetic (TM) mode grown by molecular beam epitaxy (MBE). The active layer structure consists of a 5-monolayer (ML) transition layer quantum well, double-injector-barrier and a 4-ML blocking layer. EL spectra exhibiting multiple peaks in the near-infrared region were obtained at room temperature, and the dependence of EL intensity on the injection current clearly confirmed that the emission originated from carrier injection. Moreover, a peak shift toward longer wavelengths was observed with increasing applied voltage, and preliminary estimates confirm that the magnitude of the shift is consistent with an interpretation based on the Stark effect, strongly suggesting that the emission originates from inter subband transition of intended design. • Below, we briefly describe the main achievements of this work, which we hope will clarify why this manuscript merits serious consideration for publication. • In this manuscript, we report near-infrared room temperature electroluminescence (EL) from quantum cascade laser structure using silicon (Si)/calcium fluoride (CaF 2 ) heterostructure. The optical transition layer consists of a Si quantum well, and an intersubband transition scheme is employed to achieve a significant electric dipole moment. A deep quantum well for near-infrared emission was realized using CaF 2 . In this study, due to the high barrier height of CaF 2 , the device was designed to have an emission wavelength of 1.65 μm at room temperature. • The device structure, equipped with an optical confinement waveguide and current conduction layers, was fabricated using standard LSI processes, including molecular beam epitaxy (MBE), photolithography, electron-beam lithography, and reactive ion etching, etc. These processes enable precise monolayer-level film growth and micrometer-scale fine fabrication on the SOI substrate. • The EL spectra in the near-infrared region were clearly observed at room temperature, and the dependence of the EL intensity on the injection current confirmed that the emission originated from carrier injection. A bias-dependent shift of the EL peak was observed and attributed to the Stark effect, which can be reasonably explained by the energy shift induced by the electric field applied to the Si transition quantum well in the active region.