Bound Excitons in Semiconductors

Hexagonal Boron Nitride for Next-Generation Photonics and Electronics

Hexagonal boron nitride (h-BN), an insulating 2D layered material, has recently attracted tremendous interest motivated by the extraordinary properties it shows across the fields of optoelectronics, quantum optics, and electronics, being exotic material platforms for various applications. At an early stage of h-BN research, it is explored as an ideal substrate and insulating layers for other 2D materials due to its atomically flat surface that is free of dangling bonds and charged impurities, and its high thermal conductivity. Recent discoveries of structural and optical properties of h-BN have expanded potential applications into emerging electronics and photonics fields. h-BN shows a very efficient deep-ultraviolet band-edge emission despite its indirect-bandgap nature, as well as stable room-temperature single-photon emission over a wide wavelength range, showing a great potential for next-generation photonics. In addition, h-BN is extensively being adopted as active media for low-energy electronics, including nonvolatile resistive switching memory, radio-frequency devices, and low-dielectric-constant materials for next-generation electronics.

Recent Progress on the Scanning Tunneling Microscopy and Spectroscopy Study of Semiconductor Heterojunctions

The band alignment, interface states, interface coupling, and carrier transport of semiconductor heterojunctions (SHs) need to be well understood for the design and fabrication of various important semiconductor structures and devices. Scanning tunneling microscopy (STM) with high spatial resolution and scanning tunneling spectroscopy (STS) with high energy resolution are significantly contributing to the understanding on the important properties of SHs. In this work, the recent progress on the use of STM and STS to study lateral, vertical and bulk SHs is reviewed. The spatial structures of SHs with atomically flat surface have been examined with STM. The electronic band structures (e. g., the band offset, interface state, and space charge region) of SHs are measured with STS. Combined with the spatial structures and the tunneling spectra features, the mechanism for the carrier transport in the SH may be proposed.

Coexistence of bound and localized exciton magnetic polarons in Cd(0.8)Mn(0.2)Te

Fundamental magneto-optical properties of single crystals of the semimagnetic semiconductor Cd(0.8)Mn(0.2)Te are carefully measured with the use of band-to-band excitation. Two new phenomena are presented: the peculiar magnetic field dependence of the magnetic polaron luminescence and the existence of two components for the polaron luminescence. Theoretical consideration with regard to the Zeeman effect ascribes the two components of luminescence to the exciton magnetic polaron spectrum and the neutral acceptor-bound exciton magnetic polaron spectrum. The calculated result for the luminescence peak positions is also consistent with the experimental result of the circularly polarized luminescence under the presence of an applied magnetic field. In other words, the σ(+) luminescence is due to the exciton magnetic polaron, whereas the σ(-) luminescence is due to the neutral acceptor-bound exciton magnetic polaron.