III-Nitride Digital Alloy: Electronics and Optoelectronics Properties of the InN/GaN Ultra-Short Period Superlattice Nanostructures

Abstract

The III-Nitride digital alloy (DA) is comprehensively studied as a short-period superlattice nanostructure consisting of ultra-thin III-Nitride epitaxial layers. By stacking the ultra-thin III-Nitride epitaxial layers periodically, these nanostructures are expected to have comparable optoelectronic properties as the conventional III-Nitride alloys. Here we carried out numerical studies on the InGaN DA showing the tunable optoelectronic properties of the III-Nitride DA. Our study shows that the energy gap of the InGaN DA can be tuned from ~0.63 eV up to ~2.4 eV, where the thicknesses and the thickness ratio of each GaN and InN ultra-thin binary layers within the DA structure are the key factors for tuning bandgap. Correspondingly, the absorption spectra of the InGaN DA yield broad wavelength tunability which is comparable to that of bulk InGaN ternary alloy. In addition, our investigation also reveals that the electron-hole wavefunction overlaps are remarkably large in the InGaN DA structure despite the existence of strain effect and build-in polarization field. Our findings point out the potential of III-Nitride DA as an artificially engineered nanostructure for optoelectronic device applications.

Toward three-dimensional hybrid inorganic/organic optoelectronics based on GaN/oCVD-PEDOT structures

“…In its hexagonal wurtzite crystal structure, GaN has a direct bandgap of ~3.4 eV at room temperature 30 . In combination with AlN and InN, GaN forms—in theory—a continuous alloy system whose bandgap ranges from 0.7 eV (pure InN) 31 , 32 to 6.2 eV (pure AlN) 30 .…”

Ultra-Broadband Optical Gain in III-Nitride Digital Alloys

“…The C1, HH1, and LH1 denote the ground-state conduction miniband, heavy-hole miniband, and light-hole miniband, respectively, while the HH2 is the second heavy-hole miniband. The general discussion of miniband engineering in III-Nitride DAs as function of the layer thicknesses has been presented in our previous studies 27 , 28 . The energy “width” of the miniband is determined by the span of the energy versus wave vector.…”

“…In contrast to the QW design, the III-Nitride DA consists of an ultra-short period superlattice formed by stacking ultra-thin III-Nitride epilayers periodically 27 , 28 , as shown in Fig. 1(b) .…”

“…There have been several foundational works that can be leveraged to understand and create III-Nitride digital alloys (DAs) 27 , 28 and superlattices 29 – 32 . The key behind the concept of III-Nitride DAs 27 , 28 is to employ the ultrashort period superlattices for accessing nano-engineered materials with electronic and optoelectronics properties mimicking those of alloyed systems, which also results in improved device functionality in the form of ultra-high electron-hole wavefunction overlap. In addition, there are several experimental reports of III-Nitride short-period superlattices, which show the feasibility of applying III-Nitride DA as active regions using state-of-the-art epitaxy techniques 33 – 41 .…”

Towards the indium nitride laser: obtaining infrared stimulated emission from planar monocrystalline InN structures

“…Despite this, considerable progress in device applications of epitaxial InN has been demonstrated recently, including the fabrication of infrared photodetectors 7 , thin-film transistors 8 , photovoltaic converters 9 , and a number of terahertz-range devices 10 , 11 . One of the possible ways to overcome the lattice mismatch problem is the formation of InN-based low-dimensional structures: nanowires, quantum dots, and quantum “pyramids” 12 , 13 , 14 . It has been shown that the equilibrium concentration of free carriers in nanowire structures can be reduced to ~10 13 cm −3 15 .…”