ABSTRACT
A unique design of our ultracompact microcavity wavelength conversion device exploits the simple principle that the wavelength conversion efficiency is proportional to the square of the electric field amplitude of enhanced pump light in the microcavity, and expands the range of suitable device materials to include crystals that do not exhibit birefringence or ferroelectricity. Here, as a first step toward practical applications of all-solid-state ultracompact deep-ultraviolet coherent light sources, we adopted a low-birefringence paraelectric SrB4O7 crystal with great potential for wavelength conversion and high transparency down to 130 nm as our device material, and demonstrated 234 nm deep-ultraviolet coherent light generation, whose wavelength band is expected to be used for on-demand disinfection tools that can irradiate the human body.
ABSTRACT
In this work, we demonstrate homogeneously distributed In0.3Ga0.7N/GaN quantum disks (QDs), with an average diameter below 10 nm and a high density of 2.1 × 10(11) cm(-2), embedded in 20 nm tall nanopillars. The scalable top-down fabrication process involves the use of self-assembled ferritin bio-templates as the etch mask, spin coated on top of a strained In0.3Ga0.7N/GaN single quantum well (SQW) structure, followed by a neutral beam etch (NBE) method. The small dimensions of the iron cores inside ferritin and nearly damage-free process enabled by the NBE jointly contribute to the observation of photoluminescence (PL) from strain-relaxed In0.3Ga0.7N/GaN QDs at 6 K. The large blueshift of the peak wavelength by over 70 nm manifests a strong reduction of the quantum-confined Stark effect (QCSE) within the QD structure, which also agrees well with the theoretical prediction using a 3D Schrödinger equation solver. The current results hence pave the way towards the realization of large-scale III-N quantum structures using the combination of bio-templates and NBE, which is vital for the development of next-generation lighting and communication devices.
ABSTRACT
Nearly lattice-matched In(0.528)Ga(0.472)P(1-y)Ny bulk layer and In(0.528)Ga(0.472)P(1-y)Ny/GaAs and GaAs/ In(0.528)Ga(0.472)P(1-y)Ny quantum wells with higher N content, y = 0.027, were grown on GaAs(001) substrates by metalorganic vapor phase epitaxy. High-resolution X-ray diffraction results demonstrated the high quality of both the layer and quantum wells with fairly flat interfaces. Temperature dependent photoluminescence results showed that a near-band-edge emission is dominant in the bulk In(0.528)Ga(0.472)P(0.973)N(0.027) layer, which at low temperature (T < 100 K) is associated with localized emissions centered at approximately 1.73 eV. Bandgap of In(0.528)Ga(0.472)P(0.973)N(0.027) was examined to be 1.81 and 1.78 eV at 10 K and room-temperature, respectively. Low temperature (10 K)-photoluminescence spectrum obtained from the GaAs/InxGa(1-x)P(1-y)Ny quantum well also exhibited red emission at 1.73 eV attributed to the emission from the InGaPN barrier. In addition, there are the extra weak peaks appear in a near-infrared energy range at 1.357 and 1.351 eV for InxGa(1-x)P(1-y)Ny/GaAs and GaAs/InxGa(1-x)P(1-y)Ny quantum wells, respectively. Such optical transitions are considered as an indirect transition between electrons located in the InGaPN and holes located in the GaAs regions. This situation suggested that both the In(0.528)Ga(0.472)P(0.973)N(0.027)/GaAs and GaAs/In(0.528)Ga(0.472)P(0.973)N(0.027) quantum wells exhibits a type-II quantum structure. This interpretation is justified when the valence and conduction band offsets of the type-II band alignment, which are relatively approximated to be 450 and 160 meV, are properly taken into account.