No abstract

Deep‐ultraviolet (DUV) solar‐blind communication (SBC) shows distinct advantages of non‐line‐of‐sight propagation and background noise negligibility over conventional visible‐light communication. AlGaN‐based DUV micro‐light‐emitting diodes (µ‐LEDs) are an excellent candidate for a DUV‐SBC light source due to their small size, low power consumption, and high modulation bandwidth. A long‐haul DUV‐SBC system requires the light source exhibiting high output power, high modulation bandwidth, and high rate, simultaneously. Such a device is rarely reported. A parallel‐arrayed planar (PAP) approach is here proposed to satisfy those requirements. By reducing the dimensions of the active emission mesa to micrometer scale, DUV µ‐LEDs with ultrahigh power density are created due to their homogeneous injection current and enhanced planar isotropic light emission. Interconnected PAP µ‐LEDs with a diameter of 25 µm are produced. This device has an output power of 83.5 mW with a density of 405 W cm−2 at 230 mA, a wall‐plug efficiency (WPE) of 4.7% at 155 mA, and a high −3 dB modulation bandwidth of 380 MHz. The remarkable high output power and efficiency make those devices a reliable platform to develop high‐modulation‐bandwidth wireless communication and to meet the requirements for bio‐elimination.

Quasi van der Waals epitaxy, a pioneering epitaxy of sp3‐hybridized semiconductor films on sp2‐hybridized 2D materials, provides a way, in principle, to achieve single‐crystal epilayers with preferred atom configurations that are free of substrate. Unfortunately, this has not been experimentally confirmed in the case of the hexagonal semiconductor III‐nitride epilayer until now. Here, it is reported that the epitaxy of gallium nitride (GaN) on graphene can tune the atom arrangement (lattice polarity) through manipulation of the interface atomic configuration, where GaN films with gallium and nitrogen polarity are achieved by forming CONGa(3) or COGaN(3) configurations, respectively, on artificial CO surface dangling bonds by atomic oxygen pre‐irradiation on trilayer graphene. Furthermore, an aluminum nitride buffer/interlayer leads to unique metal polarity due to the formation of an AlON thin layer in a growth environment containing trace amounts of oxygen, which explains the open question of why those reported wurtzite III‐nitride films on 2D materials always exhibit metal polarity. The reported atomic modulation through interface manipulation provides an effective model for hexagonal nitride semiconductor layers grown on graphene, which definitely promotes the development of novel semiconductor devices.

We report on a GaN/AlN quantum cascade detector operating in an extended spectral range going from the mid-infrared to visible wavelengths. This broadband detection is achieved thanks to the design of active quantum wells supporting five bound-to-bound intersubband transitions. The photodetector exhibits a broad signal between 4.1 μm and 550 nm. The photocurrent persists up to room temperature. The calibrated responsivity at 77 K under irradiation through a 45° angle polished facet amounts to 7 μA/W at a wavelength of 633 nm and is peaked at 14 μA/W at a wavelength of 720 nm.